diff --git a/beacon_node/beacon_chain/src/beacon_chain.rs b/beacon_node/beacon_chain/src/beacon_chain.rs
index 1e901987a..fb02edbe8 100644
--- a/beacon_node/beacon_chain/src/beacon_chain.rs
+++ b/beacon_node/beacon_chain/src/beacon_chain.rs
@@ -201,6 +201,9 @@ pub enum ProduceBlockVerification {
 pub struct PrePayloadAttributes {
     pub proposer_index: u64,
     pub prev_randao: Hash256,
+    /// The parent block number is not part of the payload attributes sent to the EL, but *is*
+    /// sent to builders via SSE.
+    pub parent_block_number: u64,
 }
 
 /// Define whether a forkchoiceUpdate needs to be checked for an override (`Yes`) or has already
@@ -3975,16 +3978,21 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
             proposer as u64
         };
 
-        // Get the `prev_randao` value.
-        let prev_randao = if proposer_head == parent_block_root {
-            cached_head.parent_random()
+        // Get the `prev_randao` and parent block number.
+        let head_block_number = cached_head.head_block_number()?;
+        let (prev_randao, parent_block_number) = if proposer_head == parent_block_root {
+            (
+                cached_head.parent_random()?,
+                head_block_number.saturating_sub(1),
+            )
         } else {
-            cached_head.head_random()
-        }?;
+            (cached_head.head_random()?, head_block_number)
+        };
 
         Ok(Some(PrePayloadAttributes {
             proposer_index,
             prev_randao,
+            parent_block_number,
         }))
     }
 
@@ -5059,6 +5067,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
                         proposal_slot: prepare_slot,
                         proposer_index: proposer,
                         parent_block_root: head_root,
+                        parent_block_number: pre_payload_attributes.parent_block_number,
                         parent_block_hash: forkchoice_update_params.head_hash.unwrap_or_default(),
                         payload_attributes: payload_attributes.into(),
                     },
diff --git a/beacon_node/beacon_chain/src/canonical_head.rs b/beacon_node/beacon_chain/src/canonical_head.rs
index 0d14e3819..647089f9f 100644
--- a/beacon_node/beacon_chain/src/canonical_head.rs
+++ b/beacon_node/beacon_chain/src/canonical_head.rs
@@ -167,6 +167,17 @@ impl<E: EthSpec> CachedHead<E> {
             .map(|payload| payload.prev_randao())
     }
 
+    /// Returns the execution block number of the block at the head of the chain.
+    ///
+    /// Returns an error if the chain is prior to Bellatrix.
+    pub fn head_block_number(&self) -> Result<u64, BeaconStateError> {
+        self.snapshot
+            .beacon_block
+            .message()
+            .execution_payload()
+            .map(|payload| payload.block_number())
+    }
+
     /// Returns the active validator count for the current epoch of the head state.
     ///
     /// Should only return `None` if the caches have not been built on the head state (this should
diff --git a/beacon_node/beacon_chain/src/events.rs b/beacon_node/beacon_chain/src/events.rs
index b3fa6627f..fed050323 100644
--- a/beacon_node/beacon_chain/src/events.rs
+++ b/beacon_node/beacon_chain/src/events.rs
@@ -65,43 +65,43 @@ impl<T: EthSpec> ServerSentEventHandler<T> {
             EventKind::Attestation(_) => self
                 .attestation_tx
                 .send(kind)
-                .map(|count| log_count(count, "attestation")),
+                .map(|count| log_count("attestation", count)),
             EventKind::Block(_) => self
                 .block_tx
                 .send(kind)
-                .map(|count| log_count(count, "block")),
+                .map(|count| log_count("block", count)),
             EventKind::FinalizedCheckpoint(_) => self
                 .finalized_tx
                 .send(kind)
-                .map(|count| log_count(count, "finalized checkpoint")),
+                .map(|count| log_count("finalized checkpoint", count)),
             EventKind::Head(_) => self
                 .head_tx
                 .send(kind)
-                .map(|count| log_count(count, "head")),
+                .map(|count| log_count("head", count)),
             EventKind::VoluntaryExit(_) => self
                 .exit_tx
                 .send(kind)
-                .map(|count| log_count(count, "exit")),
+                .map(|count| log_count("exit", count)),
             EventKind::ChainReorg(_) => self
                 .chain_reorg_tx
                 .send(kind)
-                .map(|count| log_count(count, "chain reorg")),
+                .map(|count| log_count("chain reorg", count)),
             EventKind::ContributionAndProof(_) => self
                 .contribution_tx
                 .send(kind)
-                .map(|count| log_count(count, "contribution and proof")),
+                .map(|count| log_count("contribution and proof", count)),
             EventKind::PayloadAttributes(_) => self
                 .payload_attributes_tx
                 .send(kind)
-                .map(|count| log_count(count, "payload attributes")),
+                .map(|count| log_count("payload attributes", count)),
             EventKind::LateHead(_) => self
                 .late_head
                 .send(kind)
-                .map(|count| log_count(count, "late head")),
+                .map(|count| log_count("late head", count)),
             EventKind::BlockReward(_) => self
                 .block_reward_tx
                 .send(kind)
-                .map(|count| log_count(count, "block reward")),
+                .map(|count| log_count("block reward", count)),
         };
         if let Err(SendError(event)) = result {
             trace!(self.log, "No receivers registered to listen for event"; "event" => ?event);
diff --git a/beacon_node/beacon_chain/src/lib.rs b/beacon_node/beacon_chain/src/lib.rs
index 9be5f13f3..fc86686bf 100644
--- a/beacon_node/beacon_chain/src/lib.rs
+++ b/beacon_node/beacon_chain/src/lib.rs
@@ -1,4 +1,3 @@
-#![recursion_limit = "128"] // For lazy-static
 pub mod attestation_rewards;
 pub mod attestation_verification;
 mod attester_cache;
diff --git a/beacon_node/beacon_chain/src/test_utils.rs b/beacon_node/beacon_chain/src/test_utils.rs
index f8dee76eb..a784c6741 100644
--- a/beacon_node/beacon_chain/src/test_utils.rs
+++ b/beacon_node/beacon_chain/src/test_utils.rs
@@ -468,7 +468,7 @@ where
         builder_threshold: Option<u128>,
     ) -> Self {
         // Get a random unused port
-        let port = unused_port::unused_tcp_port().unwrap();
+        let port = unused_port::unused_tcp4_port().unwrap();
         let builder_url = SensitiveUrl::parse(format!("http://127.0.0.1:{port}").as_str()).unwrap();
 
         let spec = self.spec.clone().expect("cannot build without spec");
diff --git a/beacon_node/client/src/lib.rs b/beacon_node/client/src/lib.rs
index b0184dc0f..584a0d736 100644
--- a/beacon_node/client/src/lib.rs
+++ b/beacon_node/client/src/lib.rs
@@ -46,9 +46,18 @@ impl<T: BeaconChainTypes> Client<T> {
         self.http_metrics_listen_addr
     }
 
-    /// Returns the port of the client's libp2p stack, if it was started.
-    pub fn libp2p_listen_port(&self) -> Option<u16> {
-        self.network_globals.as_ref().map(|n| n.listen_port_tcp())
+    /// Returns the ipv4 port of the client's libp2p stack, if it was started.
+    pub fn libp2p_listen_ipv4_port(&self) -> Option<u16> {
+        self.network_globals
+            .as_ref()
+            .and_then(|n| n.listen_port_tcp4())
+    }
+
+    /// Returns the ipv6 port of the client's libp2p stack, if it was started.
+    pub fn libp2p_listen_ipv6_port(&self) -> Option<u16> {
+        self.network_globals
+            .as_ref()
+            .and_then(|n| n.listen_port_tcp6())
     }
 
     /// Returns the list of libp2p addresses the client is listening to.
diff --git a/beacon_node/execution_layer/src/lib.rs b/beacon_node/execution_layer/src/lib.rs
index 9b6e3679a..adfdcd9f6 100644
--- a/beacon_node/execution_layer/src/lib.rs
+++ b/beacon_node/execution_layer/src/lib.rs
@@ -57,7 +57,7 @@ use types::{
 
 mod block_hash;
 mod engine_api;
-mod engines;
+pub mod engines;
 mod keccak;
 mod metrics;
 pub mod payload_cache;
@@ -342,6 +342,7 @@ impl<T: EthSpec> ExecutionLayer<T> {
                 .map_err(Error::InvalidJWTSecret)
         } else {
             // Create a new file and write a randomly generated secret to it if file does not exist
+            warn!(log, "No JWT found on disk. Generating"; "path" => %secret_file.display());
             std::fs::File::options()
                 .write(true)
                 .create_new(true)
diff --git a/beacon_node/http_api/src/lib.rs b/beacon_node/http_api/src/lib.rs
index 1065fcc8e..906f1e11d 100644
--- a/beacon_node/http_api/src/lib.rs
+++ b/beacon_node/http_api/src/lib.rs
@@ -1,4 +1,3 @@
-#![recursion_limit = "1024"]
 //! This crate contains a HTTP server which serves the endpoints listed here:
 //!
 //! https://github.com/ethereum/beacon-APIs
@@ -71,7 +70,8 @@ use warp::Reply;
 use warp::{http::Response, Filter};
 use warp_utils::{
     query::multi_key_query,
-    task::{blocking_json_task, blocking_task},
+    task::{blocking_json_task, blocking_response_task},
+    uor::UnifyingOrFilter,
 };
 
 const API_PREFIX: &str = "eth";
@@ -1125,7 +1125,7 @@ pub fn serve<T: BeaconChainTypes>(
              log: Logger| async move {
                 publish_blocks::publish_block(None, block, chain, &network_tx, log)
                     .await
-                    .map(|()| warp::reply())
+                    .map(|()| warp::reply().into_response())
             },
         );
 
@@ -1145,7 +1145,7 @@ pub fn serve<T: BeaconChainTypes>(
              log: Logger| async move {
                 publish_blocks::publish_blinded_block(block, chain, &network_tx, log)
                     .await
-                    .map(|()| warp::reply())
+                    .map(|()| warp::reply().into_response())
             },
         );
 
@@ -1251,7 +1251,7 @@ pub fn serve<T: BeaconChainTypes>(
             |block_id: BlockId,
              chain: Arc<BeaconChain<T>>,
              accept_header: Option<api_types::Accept>| {
-                blocking_task(move || {
+                blocking_response_task(move || {
                     let (block, execution_optimistic) = block_id.blinded_block(&chain)?;
                     let fork_name = block
                         .fork_name(&chain.spec)
@@ -1763,7 +1763,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(eth1_service_filter.clone())
         .and_then(
             |accept_header: Option<api_types::Accept>, eth1_service: eth1::Service| {
-                blocking_task(move || match accept_header {
+                blocking_response_task(move || match accept_header {
                     Some(api_types::Accept::Json) | None => {
                         let snapshot = eth1_service.get_deposit_snapshot();
                         Ok(
@@ -1982,7 +1982,7 @@ pub fn serve<T: BeaconChainTypes>(
              state_id: StateId,
              accept_header: Option<api_types::Accept>,
              chain: Arc<BeaconChain<T>>| {
-                blocking_task(move || match accept_header {
+                blocking_response_task(move || match accept_header {
                     Some(api_types::Accept::Ssz) => {
                         // We can ignore the optimistic status for the "fork" since it's a
                         // specification constant that doesn't change across competing heads of the
@@ -1995,7 +1995,9 @@ pub fn serve<T: BeaconChainTypes>(
                             .status(200)
                             .header("Content-Type", "application/octet-stream")
                             .body(state.as_ssz_bytes().into())
-                            .map(|resp| add_consensus_version_header(resp, fork_name))
+                            .map(|resp: warp::reply::Response| {
+                                add_consensus_version_header(resp, fork_name)
+                            })
                             .map_err(|e| {
                                 warp_utils::reject::custom_server_error(format!(
                                     "failed to create response: {}",
@@ -2158,7 +2160,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::path::end())
         .and(network_globals.clone())
         .and_then(|network_globals: Arc<NetworkGlobals<T::EthSpec>>| {
-            blocking_task(move || match *network_globals.sync_state.read() {
+            blocking_response_task(move || match *network_globals.sync_state.read() {
                 SyncState::SyncingFinalized { .. }
                 | SyncState::SyncingHead { .. }
                 | SyncState::SyncTransition
@@ -2422,7 +2424,7 @@ pub fn serve<T: BeaconChainTypes>(
                     .map_err(inconsistent_fork_rejection)?;
 
                 fork_versioned_response(endpoint_version, fork_name, block)
-                    .map(|response| warp::reply::json(&response))
+                    .map(|response| warp::reply::json(&response).into_response())
             },
         );
 
@@ -2479,7 +2481,7 @@ pub fn serve<T: BeaconChainTypes>(
 
                 // Pose as a V2 endpoint so we return the fork `version`.
                 fork_versioned_response(V2, fork_name, block)
-                    .map(|response| warp::reply::json(&response))
+                    .map(|response| warp::reply::json(&response).into_response())
             },
         );
 
@@ -2852,7 +2854,7 @@ pub fn serve<T: BeaconChainTypes>(
                         ))
                     })?;
 
-                Ok::<_, warp::reject::Rejection>(warp::reply::json(&()))
+                Ok::<_, warp::reject::Rejection>(warp::reply::json(&()).into_response())
             },
         );
 
@@ -2961,7 +2963,7 @@ pub fn serve<T: BeaconChainTypes>(
                 builder
                     .post_builder_validators(&filtered_registration_data)
                     .await
-                    .map(|resp| warp::reply::json(&resp))
+                    .map(|resp| warp::reply::json(&resp).into_response())
                     .map_err(|e| {
                         warn!(
                             log,
@@ -3223,7 +3225,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::path::end())
         .and(chain_filter.clone())
         .and_then(|chain: Arc<BeaconChain<T>>| {
-            blocking_task(move || {
+            blocking_response_task(move || {
                 Ok::<_, warp::Rejection>(warp::reply::json(&api_types::GenericResponseRef::from(
                     chain
                         .canonical_head
@@ -3342,7 +3344,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::path::end())
         .and(chain_filter.clone())
         .and_then(|state_id: StateId, chain: Arc<BeaconChain<T>>| {
-            blocking_task(move || {
+            blocking_response_task(move || {
                 // This debug endpoint provides no indication of optimistic status.
                 let (state, _execution_optimistic) = state_id.state(&chain)?;
                 Response::builder()
@@ -3478,9 +3480,10 @@ pub fn serve<T: BeaconChainTypes>(
         .and(chain_filter.clone())
         .and_then(|chain: Arc<BeaconChain<T>>| async move {
             let merge_readiness = chain.check_merge_readiness().await;
-            Ok::<_, warp::reject::Rejection>(warp::reply::json(&api_types::GenericResponse::from(
-                merge_readiness,
-            )))
+            Ok::<_, warp::reject::Rejection>(
+                warp::reply::json(&api_types::GenericResponse::from(merge_readiness))
+                    .into_response(),
+            )
         });
 
     // GET lighthouse/beacon/blobs_sidecars/{block_id}
@@ -3526,7 +3529,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and_then(
             |topics_res: Result<api_types::EventQuery, warp::Rejection>,
              chain: Arc<BeaconChain<T>>| {
-                blocking_task(move || {
+                blocking_response_task(move || {
                     let topics = topics_res?;
                     // for each topic subscribed spawn a new subscription
                     let mut receivers = Vec::with_capacity(topics.topics.len());
@@ -3593,109 +3596,110 @@ pub fn serve<T: BeaconChainTypes>(
         );
 
     // Define the ultimate set of routes that will be provided to the server.
+    // Use `uor` rather than `or` in order to simplify types (see `UnifyingOrFilter`).
     let routes = warp::get()
         .and(
             get_beacon_genesis
-                .boxed()
-                .or(get_beacon_state_root.boxed())
-                .or(get_beacon_state_fork.boxed())
-                .or(get_beacon_state_finality_checkpoints.boxed())
-                .or(get_beacon_state_validator_balances.boxed())
-                .or(get_beacon_state_validators_id.boxed())
-                .or(get_beacon_state_validators.boxed())
-                .or(get_beacon_state_committees.boxed())
-                .or(get_beacon_state_sync_committees.boxed())
-                .or(get_beacon_state_randao.boxed())
-                .or(get_beacon_headers.boxed())
-                .or(get_beacon_headers_block_id.boxed())
-                .or(get_beacon_block.boxed())
-                .or(get_beacon_block_attestations.boxed())
-                .or(get_beacon_blinded_block.boxed())
-                .or(get_beacon_block_root.boxed())
-                .or(get_beacon_pool_attestations.boxed())
-                .or(get_beacon_pool_attester_slashings.boxed())
-                .or(get_beacon_pool_proposer_slashings.boxed())
-                .or(get_beacon_pool_voluntary_exits.boxed())
-                .or(get_beacon_pool_bls_to_execution_changes.boxed())
-                .or(get_beacon_deposit_snapshot.boxed())
-                .or(get_beacon_rewards_blocks.boxed())
-                .or(get_config_fork_schedule.boxed())
-                .or(get_config_spec.boxed())
-                .or(get_config_deposit_contract.boxed())
-                .or(get_debug_beacon_states.boxed())
-                .or(get_debug_beacon_heads.boxed())
-                .or(get_node_identity.boxed())
-                .or(get_node_version.boxed())
-                .or(get_node_syncing.boxed())
-                .or(get_node_health.boxed())
-                .or(get_node_peers_by_id.boxed())
-                .or(get_node_peers.boxed())
-                .or(get_node_peer_count.boxed())
-                .or(get_validator_duties_proposer.boxed())
-                .or(get_validator_blocks.boxed())
-                .or(get_validator_blinded_blocks.boxed())
-                .or(get_validator_attestation_data.boxed())
-                .or(get_validator_aggregate_attestation.boxed())
-                .or(get_validator_sync_committee_contribution.boxed())
-                .or(get_lighthouse_health.boxed())
-                .or(get_lighthouse_ui_health.boxed())
-                .or(get_lighthouse_ui_validator_count.boxed())
-                .or(get_lighthouse_syncing.boxed())
-                .or(get_lighthouse_nat.boxed())
-                .or(get_lighthouse_peers.boxed())
-                .or(get_lighthouse_peers_connected.boxed())
-                .or(get_lighthouse_proto_array.boxed())
-                .or(get_lighthouse_validator_inclusion_global.boxed())
-                .or(get_lighthouse_validator_inclusion.boxed())
-                .or(get_lighthouse_eth1_syncing.boxed())
-                .or(get_lighthouse_eth1_block_cache.boxed())
-                .or(get_lighthouse_eth1_deposit_cache.boxed())
-                .or(get_lighthouse_beacon_states_ssz.boxed())
-                .or(get_lighthouse_staking.boxed())
-                .or(get_lighthouse_database_info.boxed())
-                .or(get_lighthouse_block_rewards.boxed())
-                .or(get_lighthouse_attestation_performance.boxed())
-                .or(get_lighthouse_block_packing_efficiency.boxed())
-                .or(get_lighthouse_merge_readiness.boxed())
-                .or(get_lighthouse_blobs_sidecars.boxed())
-                .or(get_events.boxed())
+                .uor(get_beacon_state_root)
+                .uor(get_beacon_state_fork)
+                .uor(get_beacon_state_finality_checkpoints)
+                .uor(get_beacon_state_validator_balances)
+                .uor(get_beacon_state_validators_id)
+                .uor(get_beacon_state_validators)
+                .uor(get_beacon_state_committees)
+                .uor(get_beacon_state_sync_committees)
+                .uor(get_beacon_state_randao)
+                .uor(get_beacon_headers)
+                .uor(get_beacon_headers_block_id)
+                .uor(get_beacon_block)
+                .uor(get_beacon_block_attestations)
+                .uor(get_beacon_blinded_block)
+                .uor(get_beacon_block_root)
+                .uor(get_beacon_pool_attestations)
+                .uor(get_beacon_pool_attester_slashings)
+                .uor(get_beacon_pool_proposer_slashings)
+                .uor(get_beacon_pool_voluntary_exits)
+                .uor(get_beacon_pool_bls_to_execution_changes)
+                .uor(get_beacon_deposit_snapshot)
+                .uor(get_beacon_rewards_blocks)
+                .uor(get_config_fork_schedule)
+                .uor(get_config_spec)
+                .uor(get_config_deposit_contract)
+                .uor(get_debug_beacon_states)
+                .uor(get_debug_beacon_heads)
+                .uor(get_node_identity)
+                .uor(get_node_version)
+                .uor(get_node_syncing)
+                .uor(get_node_health)
+                .uor(get_node_peers_by_id)
+                .uor(get_node_peers)
+                .uor(get_node_peer_count)
+                .uor(get_validator_duties_proposer)
+                .uor(get_validator_blocks)
+                .uor(get_validator_blinded_blocks)
+                .uor(get_validator_attestation_data)
+                .uor(get_validator_aggregate_attestation)
+                .uor(get_validator_sync_committee_contribution)
+                .uor(get_lighthouse_health)
+                .uor(get_lighthouse_ui_health)
+                .uor(get_lighthouse_ui_validator_count)
+                .uor(get_lighthouse_syncing)
+                .uor(get_lighthouse_nat)
+                .uor(get_lighthouse_peers)
+                .uor(get_lighthouse_peers_connected)
+                .uor(get_lighthouse_proto_array)
+                .uor(get_lighthouse_validator_inclusion_global)
+                .uor(get_lighthouse_validator_inclusion)
+                .uor(get_lighthouse_eth1_syncing)
+                .uor(get_lighthouse_eth1_block_cache)
+                .uor(get_lighthouse_eth1_deposit_cache)
+                .uor(get_lighthouse_beacon_states_ssz)
+                .uor(get_lighthouse_staking)
+                .uor(get_lighthouse_database_info)
+                .uor(get_lighthouse_block_rewards)
+                .uor(get_lighthouse_attestation_performance)
+                .uor(get_lighthouse_block_packing_efficiency)
+                .uor(get_lighthouse_merge_readiness)
+                .uor(get_events)
                 .recover(warp_utils::reject::handle_rejection),
         )
         .boxed()
-        .or(warp::post().and(
-            post_beacon_blocks
-                .boxed()
-                .or(post_beacon_blinded_blocks.boxed())
-                .or(post_beacon_pool_attestations.boxed())
-                .or(post_beacon_pool_attester_slashings.boxed())
-                .or(post_beacon_pool_proposer_slashings.boxed())
-                .or(post_beacon_pool_voluntary_exits.boxed())
-                .or(post_beacon_pool_sync_committees.boxed())
-                .or(post_beacon_pool_bls_to_execution_changes.boxed())
-                .or(post_beacon_rewards_attestations.boxed())
-                .or(post_beacon_rewards_sync_committee.boxed())
-                .or(post_validator_duties_attester.boxed())
-                .or(post_validator_duties_sync.boxed())
-                .or(post_validator_aggregate_and_proofs.boxed())
-                .or(post_validator_contribution_and_proofs.boxed())
-                .or(post_validator_beacon_committee_subscriptions.boxed())
-                .or(post_validator_sync_committee_subscriptions.boxed())
-                .or(post_validator_prepare_beacon_proposer.boxed())
-                .or(post_validator_register_validator.boxed())
-                .or(post_lighthouse_liveness.boxed())
-                .or(post_lighthouse_database_reconstruct.boxed())
-                .or(post_lighthouse_database_historical_blocks.boxed())
-                .or(post_lighthouse_block_rewards.boxed())
-                .or(post_lighthouse_ui_validator_metrics.boxed())
-                .or(post_lighthouse_ui_validator_info.boxed())
-                .recover(warp_utils::reject::handle_rejection),
-        ))
+        .uor(
+            warp::post().and(
+                post_beacon_blocks
+                    .uor(post_beacon_blinded_blocks)
+                    .uor(post_beacon_pool_attestations)
+                    .uor(post_beacon_pool_attester_slashings)
+                    .uor(post_beacon_pool_proposer_slashings)
+                    .uor(post_beacon_pool_voluntary_exits)
+                    .uor(post_beacon_pool_sync_committees)
+                    .uor(post_beacon_pool_bls_to_execution_changes)
+                    .uor(post_beacon_rewards_attestations)
+                    .uor(post_beacon_rewards_sync_committee)
+                    .uor(post_validator_duties_attester)
+                    .uor(post_validator_duties_sync)
+                    .uor(post_validator_aggregate_and_proofs)
+                    .uor(post_validator_contribution_and_proofs)
+                    .uor(post_validator_beacon_committee_subscriptions)
+                    .uor(post_validator_sync_committee_subscriptions)
+                    .uor(post_validator_prepare_beacon_proposer)
+                    .uor(post_validator_register_validator)
+                    .uor(post_lighthouse_liveness)
+                    .uor(post_lighthouse_database_reconstruct)
+                    .uor(post_lighthouse_database_historical_blocks)
+                    .uor(post_lighthouse_block_rewards)
+                    .uor(post_lighthouse_ui_validator_metrics)
+                    .uor(post_lighthouse_ui_validator_info)
+                    .recover(warp_utils::reject::handle_rejection),
+            ),
+        )
         .recover(warp_utils::reject::handle_rejection)
         .with(slog_logging(log.clone()))
         .with(prometheus_metrics())
         // Add a `Server` header.
         .map(|reply| warp::reply::with_header(reply, "Server", &version_with_platform()))
-        .with(cors_builder.build());
+        .with(cors_builder.build())
+        .boxed();
 
     let http_socket: SocketAddr = SocketAddr::new(config.listen_addr, config.listen_port);
     let http_server: HttpServer = match config.tls_config {
diff --git a/beacon_node/http_api/src/version.rs b/beacon_node/http_api/src/version.rs
index 30f475e68..e7fd8910b 100644
--- a/beacon_node/http_api/src/version.rs
+++ b/beacon_node/http_api/src/version.rs
@@ -4,7 +4,7 @@ use serde::Serialize;
 use types::{
     ExecutionOptimisticForkVersionedResponse, ForkName, ForkVersionedResponse, InconsistentFork,
 };
-use warp::reply::{self, Reply, WithHeader};
+use warp::reply::{self, Reply, Response};
 
 pub const V1: EndpointVersion = EndpointVersion(1);
 pub const V2: EndpointVersion = EndpointVersion(2);
@@ -48,8 +48,8 @@ pub fn execution_optimistic_fork_versioned_response<T: Serialize>(
 }
 
 /// Add the `Eth-Consensus-Version` header to a response.
-pub fn add_consensus_version_header<T: Reply>(reply: T, fork_name: ForkName) -> WithHeader<T> {
-    reply::with_header(reply, CONSENSUS_VERSION_HEADER, fork_name.to_string())
+pub fn add_consensus_version_header<T: Reply>(reply: T, fork_name: ForkName) -> Response {
+    reply::with_header(reply, CONSENSUS_VERSION_HEADER, fork_name.to_string()).into_response()
 }
 
 pub fn inconsistent_fork_rejection(error: InconsistentFork) -> warp::reject::Rejection {
diff --git a/beacon_node/http_api/tests/common.rs b/beacon_node/http_api/tests/common.rs
index d0eabcc26..9fe26c0e8 100644
--- a/beacon_node/http_api/tests/common.rs
+++ b/beacon_node/http_api/tests/common.rs
@@ -127,7 +127,7 @@ pub async fn create_api_server<T: BeaconChainTypes>(
     log: Logger,
 ) -> ApiServer<T::EthSpec, impl Future<Output = ()>> {
     // Get a random unused port.
-    let port = unused_port::unused_tcp_port().unwrap();
+    let port = unused_port::unused_tcp4_port().unwrap();
     create_api_server_on_port(chain, log, port).await
 }
 
@@ -148,8 +148,8 @@ pub async fn create_api_server_on_port<T: BeaconChainTypes>(
     let enr = EnrBuilder::new("v4").build(&enr_key).unwrap();
     let network_globals = Arc::new(NetworkGlobals::new(
         enr.clone(),
-        TCP_PORT,
-        UDP_PORT,
+        Some(TCP_PORT),
+        None,
         meta_data,
         vec![],
         &log,
diff --git a/beacon_node/http_api/tests/main.rs b/beacon_node/http_api/tests/main.rs
index 76a851dc4..88e0032ec 100644
--- a/beacon_node/http_api/tests/main.rs
+++ b/beacon_node/http_api/tests/main.rs
@@ -1,5 +1,4 @@
 #![cfg(not(debug_assertions))] // Tests are too slow in debug.
-#![recursion_limit = "512"]
 
 pub mod common;
 pub mod fork_tests;
diff --git a/beacon_node/http_api/tests/tests.rs b/beacon_node/http_api/tests/tests.rs
index 6424d73eb..977c737fd 100644
--- a/beacon_node/http_api/tests/tests.rs
+++ b/beacon_node/http_api/tests/tests.rs
@@ -112,7 +112,7 @@ impl ApiTester {
     pub async fn new_from_config(config: ApiTesterConfig) -> Self {
         // Get a random unused port
         let spec = config.spec;
-        let port = unused_port::unused_tcp_port().unwrap();
+        let port = unused_port::unused_tcp4_port().unwrap();
         let beacon_url = SensitiveUrl::parse(format!("http://127.0.0.1:{port}").as_str()).unwrap();
 
         let harness = Arc::new(
diff --git a/beacon_node/lighthouse_network/src/config.rs b/beacon_node/lighthouse_network/src/config.rs
index e40384332..79c8b67d7 100644
--- a/beacon_node/lighthouse_network/src/config.rs
+++ b/beacon_node/lighthouse_network/src/config.rs
@@ -1,3 +1,4 @@
+use crate::listen_addr::{ListenAddr, ListenAddress};
 use crate::rpc::config::OutboundRateLimiterConfig;
 use crate::types::GossipKind;
 use crate::{Enr, PeerIdSerialized};
@@ -12,6 +13,7 @@ use libp2p::gossipsub::{
 use libp2p::Multiaddr;
 use serde_derive::{Deserialize, Serialize};
 use sha2::{Digest, Sha256};
+use std::net::{Ipv4Addr, Ipv6Addr};
 use std::path::PathBuf;
 use std::sync::Arc;
 use std::time::Duration;
@@ -57,24 +59,24 @@ pub struct Config {
     /// Data directory where node's keyfile is stored
     pub network_dir: PathBuf,
 
-    /// IP address to listen on.
-    pub listen_address: std::net::IpAddr,
-
-    /// The TCP port that libp2p listens on.
-    pub libp2p_port: u16,
-
-    /// UDP port that discovery listens on.
-    pub discovery_port: u16,
+    /// IP addresses to listen on.
+    listen_addresses: ListenAddress,
 
     /// The address to broadcast to peers about which address we are listening on. None indicates
     /// that no discovery address has been set in the CLI args.
-    pub enr_address: Option<std::net::IpAddr>,
+    pub enr_address: (Option<Ipv4Addr>, Option<Ipv6Addr>),
 
-    /// The udp port to broadcast to peers in order to reach back for discovery.
-    pub enr_udp_port: Option<u16>,
+    /// The udp4 port to broadcast to peers in order to reach back for discovery.
+    pub enr_udp4_port: Option<u16>,
 
-    /// The tcp port to broadcast to peers in order to reach back for libp2p services.
-    pub enr_tcp_port: Option<u16>,
+    /// The tcp4 port to broadcast to peers in order to reach back for libp2p services.
+    pub enr_tcp4_port: Option<u16>,
+
+    /// The udp6 port to broadcast to peers in order to reach back for discovery.
+    pub enr_udp6_port: Option<u16>,
+
+    /// The tcp6 port to broadcast to peers in order to reach back for libp2p services.
+    pub enr_tcp6_port: Option<u16>,
 
     /// Target number of connected peers.
     pub target_peers: usize,
@@ -139,6 +141,105 @@ pub struct Config {
     pub outbound_rate_limiter_config: Option<OutboundRateLimiterConfig>,
 }
 
+impl Config {
+    /// Sets the listening address to use an ipv4 address. The discv5 ip_mode and table filter are
+    /// adjusted accordingly to ensure addresses that are present in the enr are globally
+    /// reachable.
+    pub fn set_ipv4_listening_address(&mut self, addr: Ipv4Addr, tcp_port: u16, udp_port: u16) {
+        self.listen_addresses = ListenAddress::V4(ListenAddr {
+            addr,
+            udp_port,
+            tcp_port,
+        });
+        self.discv5_config.ip_mode = discv5::IpMode::Ip4;
+        self.discv5_config.table_filter = |enr| enr.ip4().as_ref().map_or(false, is_global_ipv4)
+    }
+
+    /// Sets the listening address to use an ipv6 address. The discv5 ip_mode and table filter is
+    /// adjusted accordingly to ensure addresses that are present in the enr are globally
+    /// reachable.
+    pub fn set_ipv6_listening_address(&mut self, addr: Ipv6Addr, tcp_port: u16, udp_port: u16) {
+        self.listen_addresses = ListenAddress::V6(ListenAddr {
+            addr,
+            udp_port,
+            tcp_port,
+        });
+        self.discv5_config.ip_mode = discv5::IpMode::Ip6 {
+            enable_mapped_addresses: false,
+        };
+        self.discv5_config.table_filter = |enr| enr.ip6().as_ref().map_or(false, is_global_ipv6)
+    }
+
+    /// Sets the listening address to use both an ipv4 and ipv6 address. The discv5 ip_mode and
+    /// table filter is adjusted accordingly to ensure addresses that are present in the enr are
+    /// globally reachable.
+    pub fn set_ipv4_ipv6_listening_addresses(
+        &mut self,
+        v4_addr: Ipv4Addr,
+        tcp4_port: u16,
+        udp4_port: u16,
+        v6_addr: Ipv6Addr,
+        tcp6_port: u16,
+        udp6_port: u16,
+    ) {
+        self.listen_addresses = ListenAddress::DualStack(
+            ListenAddr {
+                addr: v4_addr,
+                udp_port: udp4_port,
+                tcp_port: tcp4_port,
+            },
+            ListenAddr {
+                addr: v6_addr,
+                udp_port: udp6_port,
+                tcp_port: tcp6_port,
+            },
+        );
+
+        self.discv5_config.ip_mode = discv5::IpMode::Ip6 {
+            enable_mapped_addresses: true,
+        };
+        self.discv5_config.table_filter = |enr| match (&enr.ip4(), &enr.ip6()) {
+            (None, None) => false,
+            (None, Some(ip6)) => is_global_ipv6(ip6),
+            (Some(ip4), None) => is_global_ipv4(ip4),
+            (Some(ip4), Some(ip6)) => is_global_ipv4(ip4) && is_global_ipv6(ip6),
+        };
+    }
+
+    pub fn set_listening_addr(&mut self, listen_addr: ListenAddress) {
+        match listen_addr {
+            ListenAddress::V4(ListenAddr {
+                addr,
+                udp_port,
+                tcp_port,
+            }) => self.set_ipv4_listening_address(addr, tcp_port, udp_port),
+            ListenAddress::V6(ListenAddr {
+                addr,
+                udp_port,
+                tcp_port,
+            }) => self.set_ipv6_listening_address(addr, tcp_port, udp_port),
+            ListenAddress::DualStack(
+                ListenAddr {
+                    addr: ip4addr,
+                    udp_port: udp4_port,
+                    tcp_port: tcp4_port,
+                },
+                ListenAddr {
+                    addr: ip6addr,
+                    udp_port: udp6_port,
+                    tcp_port: tcp6_port,
+                },
+            ) => self.set_ipv4_ipv6_listening_addresses(
+                ip4addr, tcp4_port, udp4_port, ip6addr, tcp6_port, udp6_port,
+            ),
+        }
+    }
+
+    pub fn listen_addrs(&self) -> &ListenAddress {
+        &self.listen_addresses
+    }
+}
+
 impl Default for Config {
     /// Generate a default network configuration.
     fn default() -> Self {
@@ -183,7 +284,7 @@ impl Default for Config {
             .filter_rate_limiter(filter_rate_limiter)
             .filter_max_bans_per_ip(Some(5))
             .filter_max_nodes_per_ip(Some(10))
-            .table_filter(|enr| enr.ip4().map_or(false, |ip| is_global(&ip))) // Filter non-global IPs
+            .table_filter(|enr| enr.ip4().map_or(false, |ip| is_global_ipv4(&ip))) // Filter non-global IPs
             .ban_duration(Some(Duration::from_secs(3600)))
             .ping_interval(Duration::from_secs(300))
             .build();
@@ -191,12 +292,16 @@ impl Default for Config {
         // NOTE: Some of these get overridden by the corresponding CLI default values.
         Config {
             network_dir,
-            listen_address: "0.0.0.0".parse().expect("valid ip address"),
-            libp2p_port: 9000,
-            discovery_port: 9000,
-            enr_address: None,
-            enr_udp_port: None,
-            enr_tcp_port: None,
+            listen_addresses: ListenAddress::V4(ListenAddr {
+                addr: Ipv4Addr::UNSPECIFIED,
+                udp_port: 9000,
+                tcp_port: 9000,
+            }),
+            enr_address: (None, None),
+            enr_udp4_port: None,
+            enr_tcp4_port: None,
+            enr_udp6_port: None,
+            enr_tcp6_port: None,
             target_peers: 50,
             gs_config,
             discv5_config,
@@ -363,7 +468,7 @@ pub fn gossipsub_config(network_load: u8, fork_context: Arc<ForkContext>) -> Gos
 /// Helper function to determine if the IpAddr is a global address or not. The `is_global()`
 /// function is not yet stable on IpAddr.
 #[allow(clippy::nonminimal_bool)]
-fn is_global(addr: &std::net::Ipv4Addr) -> bool {
+fn is_global_ipv4(addr: &Ipv4Addr) -> bool {
     // check if this address is 192.0.0.9 or 192.0.0.10. These addresses are the only two
     // globally routable addresses in the 192.0.0.0/24 range.
     if u32::from_be_bytes(addr.octets()) == 0xc0000009
@@ -384,3 +489,60 @@ fn is_global(addr: &std::net::Ipv4Addr) -> bool {
             // Make sure the address is not in 0.0.0.0/8
             && addr.octets()[0] != 0
 }
+
+/// NOTE: Docs taken from https://doc.rust-lang.org/stable/std/net/struct.Ipv6Addr.html#method.is_global
+///
+/// Returns true if the address appears to be globally reachable as specified by the IANA IPv6
+/// Special-Purpose Address Registry. Whether or not an address is practically reachable will
+/// depend on your network configuration.
+///
+/// Most IPv6 addresses are globally reachable; unless they are specifically defined as not
+/// globally reachable.
+///
+/// Non-exhaustive list of notable addresses that are not globally reachable:
+///
+/// - The unspecified address (is_unspecified)
+/// - The loopback address (is_loopback)
+/// - IPv4-mapped addresses
+/// - Addresses reserved for benchmarking
+/// - Addresses reserved for documentation (is_documentation)
+/// - Unique local addresses (is_unique_local)
+/// - Unicast addresses with link-local scope (is_unicast_link_local)
+// TODO: replace with [`Ipv6Addr::is_global`] once
+//       [Ip](https://github.com/rust-lang/rust/issues/27709) is stable.
+pub const fn is_global_ipv6(addr: &Ipv6Addr) -> bool {
+    const fn is_documentation(addr: &Ipv6Addr) -> bool {
+        (addr.segments()[0] == 0x2001) && (addr.segments()[1] == 0xdb8)
+    }
+    const fn is_unique_local(addr: &Ipv6Addr) -> bool {
+        (addr.segments()[0] & 0xfe00) == 0xfc00
+    }
+    const fn is_unicast_link_local(addr: &Ipv6Addr) -> bool {
+        (addr.segments()[0] & 0xffc0) == 0xfe80
+    }
+    !(addr.is_unspecified()
+            || addr.is_loopback()
+            // IPv4-mapped Address (`::ffff:0:0/96`)
+            || matches!(addr.segments(), [0, 0, 0, 0, 0, 0xffff, _, _])
+            // IPv4-IPv6 Translat. (`64:ff9b:1::/48`)
+            || matches!(addr.segments(), [0x64, 0xff9b, 1, _, _, _, _, _])
+            // Discard-Only Address Block (`100::/64`)
+            || matches!(addr.segments(), [0x100, 0, 0, 0, _, _, _, _])
+            // IETF Protocol Assignments (`2001::/23`)
+            || (matches!(addr.segments(), [0x2001, b, _, _, _, _, _, _] if b < 0x200)
+                && !(
+                    // Port Control Protocol Anycast (`2001:1::1`)
+                    u128::from_be_bytes(addr.octets()) == 0x2001_0001_0000_0000_0000_0000_0000_0001
+                    // Traversal Using Relays around NAT Anycast (`2001:1::2`)
+                    || u128::from_be_bytes(addr.octets()) == 0x2001_0001_0000_0000_0000_0000_0000_0002
+                    // AMT (`2001:3::/32`)
+                    || matches!(addr.segments(), [0x2001, 3, _, _, _, _, _, _])
+                    // AS112-v6 (`2001:4:112::/48`)
+                    || matches!(addr.segments(), [0x2001, 4, 0x112, _, _, _, _, _])
+                    // ORCHIDv2 (`2001:20::/28`)
+                    || matches!(addr.segments(), [0x2001, b, _, _, _, _, _, _] if b >= 0x20 && b <= 0x2F)
+                ))
+            || is_documentation(addr)
+            || is_unique_local(addr)
+            || is_unicast_link_local(addr))
+}
diff --git a/beacon_node/lighthouse_network/src/discovery/enr.rs b/beacon_node/lighthouse_network/src/discovery/enr.rs
index 6b4b87a5f..938e7cfa2 100644
--- a/beacon_node/lighthouse_network/src/discovery/enr.rs
+++ b/beacon_node/lighthouse_network/src/discovery/enr.rs
@@ -145,16 +145,39 @@ pub fn create_enr_builder_from_config<T: EnrKey>(
     enable_tcp: bool,
 ) -> EnrBuilder<T> {
     let mut builder = EnrBuilder::new("v4");
-    if let Some(enr_address) = config.enr_address {
-        builder.ip(enr_address);
+    let (maybe_ipv4_address, maybe_ipv6_address) = &config.enr_address;
+
+    if let Some(ip) = maybe_ipv4_address {
+        builder.ip4(*ip);
     }
-    if let Some(udp_port) = config.enr_udp_port {
-        builder.udp4(udp_port);
+
+    if let Some(ip) = maybe_ipv6_address {
+        builder.ip6(*ip);
     }
-    // we always give it our listening tcp port
+
+    if let Some(udp4_port) = config.enr_udp4_port {
+        builder.udp4(udp4_port);
+    }
+
+    if let Some(udp6_port) = config.enr_udp6_port {
+        builder.udp6(udp6_port);
+    }
+
     if enable_tcp {
-        let tcp_port = config.enr_tcp_port.unwrap_or(config.libp2p_port);
-        builder.tcp4(tcp_port);
+        // If the ENR port is not set, and we are listening over that ip version, use the listening port instead.
+        let tcp4_port = config
+            .enr_tcp4_port
+            .or_else(|| config.listen_addrs().v4().map(|v4_addr| v4_addr.tcp_port));
+        if let Some(tcp4_port) = tcp4_port {
+            builder.tcp4(tcp4_port);
+        }
+
+        let tcp6_port = config
+            .enr_tcp6_port
+            .or_else(|| config.listen_addrs().v6().map(|v6_addr| v6_addr.tcp_port));
+        if let Some(tcp6_port) = tcp6_port {
+            builder.tcp6(tcp6_port);
+        }
     }
     builder
 }
diff --git a/beacon_node/lighthouse_network/src/discovery/mod.rs b/beacon_node/lighthouse_network/src/discovery/mod.rs
index c41844c2c..b9c4e76fe 100644
--- a/beacon_node/lighthouse_network/src/discovery/mod.rs
+++ b/beacon_node/lighthouse_network/src/discovery/mod.rs
@@ -201,8 +201,13 @@ impl<TSpec: EthSpec> Discovery<TSpec> {
         info!(log, "ENR Initialised"; "enr" => local_enr.to_base64(), "seq" => local_enr.seq(), "id"=> %local_enr.node_id(),
               "ip4" => ?local_enr.ip4(), "udp4"=> ?local_enr.udp4(), "tcp4" => ?local_enr.tcp6()
         );
-
-        let listen_socket = SocketAddr::new(config.listen_address, config.discovery_port);
+        let listen_socket = match config.listen_addrs() {
+            crate::listen_addr::ListenAddress::V4(v4_addr) => v4_addr.udp_socket_addr(),
+            crate::listen_addr::ListenAddress::V6(v6_addr) => v6_addr.udp_socket_addr(),
+            crate::listen_addr::ListenAddress::DualStack(_v4_addr, v6_addr) => {
+                v6_addr.udp_socket_addr()
+            }
+        };
 
         // convert the keypair into an ENR key
         let enr_key: CombinedKey = CombinedKey::from_libp2p(local_key)?;
@@ -1015,14 +1020,27 @@ impl<TSpec: EthSpec> NetworkBehaviour for Discovery<TSpec> {
                             *self.network_globals.local_enr.write() = enr;
                             // A new UDP socket has been detected.
                             // Build a multiaddr to report to libp2p
-                            let mut address = Multiaddr::from(socket_addr.ip());
-                            // NOTE: This doesn't actually track the external TCP port. More sophisticated NAT handling
-                            // should handle this.
-                            address.push(Protocol::Tcp(self.network_globals.listen_port_tcp()));
-                            return Poll::Ready(NBAction::ReportObservedAddr {
-                                address,
-                                score: AddressScore::Finite(1),
-                            });
+                            let addr = match socket_addr.ip() {
+                                IpAddr::V4(v4_addr) => {
+                                    self.network_globals.listen_port_tcp4().map(|tcp4_port| {
+                                        Multiaddr::from(v4_addr).with(Protocol::Tcp(tcp4_port))
+                                    })
+                                }
+                                IpAddr::V6(v6_addr) => {
+                                    self.network_globals.listen_port_tcp6().map(|tcp6_port| {
+                                        Multiaddr::from(v6_addr).with(Protocol::Tcp(tcp6_port))
+                                    })
+                                }
+                            };
+
+                            if let Some(address) = addr {
+                                // NOTE: This doesn't actually track the external TCP port. More sophisticated NAT handling
+                                // should handle this.
+                                return Poll::Ready(NBAction::ReportObservedAddr {
+                                    address,
+                                    score: AddressScore::Finite(1),
+                                });
+                            }
                         }
                         Discv5Event::EnrAdded { .. }
                         | Discv5Event::TalkRequest(_)
@@ -1087,7 +1105,6 @@ mod tests {
     use enr::EnrBuilder;
     use slog::{o, Drain};
     use types::{BitVector, MinimalEthSpec, SubnetId};
-    use unused_port::unused_udp_port;
 
     type E = MinimalEthSpec;
 
@@ -1105,17 +1122,15 @@ mod tests {
 
     async fn build_discovery() -> Discovery<E> {
         let keypair = libp2p::identity::Keypair::generate_secp256k1();
-        let config = NetworkConfig {
-            discovery_port: unused_udp_port().unwrap(),
-            ..Default::default()
-        };
+        let mut config = NetworkConfig::default();
+        config.set_listening_addr(crate::ListenAddress::unused_v4_ports());
         let enr_key: CombinedKey = CombinedKey::from_libp2p(&keypair).unwrap();
         let enr: Enr = build_enr::<E>(&enr_key, &config, &EnrForkId::default()).unwrap();
         let log = build_log(slog::Level::Debug, false);
         let globals = NetworkGlobals::new(
             enr,
-            9000,
-            9000,
+            Some(9000),
+            None,
             MetaData::V2(MetaDataV2 {
                 seq_number: 0,
                 attnets: Default::default(),
diff --git a/beacon_node/lighthouse_network/src/lib.rs b/beacon_node/lighthouse_network/src/lib.rs
index be4da809c..3d539af3b 100644
--- a/beacon_node/lighthouse_network/src/lib.rs
+++ b/beacon_node/lighthouse_network/src/lib.rs
@@ -10,12 +10,14 @@ pub mod service;
 
 #[allow(clippy::mutable_key_type)] // PeerId in hashmaps are no longer permitted by clippy
 pub mod discovery;
+pub mod listen_addr;
 pub mod metrics;
 pub mod peer_manager;
 pub mod rpc;
 pub mod types;
 
 pub use config::gossip_max_size;
+pub use listen_addr::*;
 
 use serde::{de, Deserialize, Deserializer, Serialize, Serializer};
 use std::str::FromStr;
diff --git a/beacon_node/lighthouse_network/src/listen_addr.rs b/beacon_node/lighthouse_network/src/listen_addr.rs
new file mode 100644
index 000000000..20d87d403
--- /dev/null
+++ b/beacon_node/lighthouse_network/src/listen_addr.rs
@@ -0,0 +1,97 @@
+use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr};
+
+use libp2p::{multiaddr::Protocol, Multiaddr};
+use serde::{Deserialize, Serialize};
+
+/// A listening address composed by an Ip, an UDP port and a TCP port.
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub struct ListenAddr<Ip> {
+    pub addr: Ip,
+    pub udp_port: u16,
+    pub tcp_port: u16,
+}
+
+impl<Ip: Into<IpAddr> + Clone> ListenAddr<Ip> {
+    pub fn udp_socket_addr(&self) -> SocketAddr {
+        (self.addr.clone().into(), self.udp_port).into()
+    }
+
+    pub fn tcp_socket_addr(&self) -> SocketAddr {
+        (self.addr.clone().into(), self.tcp_port).into()
+    }
+}
+
+/// Types of listening addresses Lighthouse can accept.
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub enum ListenAddress {
+    V4(ListenAddr<Ipv4Addr>),
+    V6(ListenAddr<Ipv6Addr>),
+    DualStack(ListenAddr<Ipv4Addr>, ListenAddr<Ipv6Addr>),
+}
+
+impl ListenAddress {
+    /// Return the listening address over IpV4 if any.
+    pub fn v4(&self) -> Option<&ListenAddr<Ipv4Addr>> {
+        match self {
+            ListenAddress::V4(v4_addr) | ListenAddress::DualStack(v4_addr, _) => Some(v4_addr),
+            ListenAddress::V6(_) => None,
+        }
+    }
+
+    /// Return the listening address over IpV6 if any.
+    pub fn v6(&self) -> Option<&ListenAddr<Ipv6Addr>> {
+        match self {
+            ListenAddress::V6(v6_addr) | ListenAddress::DualStack(_, v6_addr) => Some(v6_addr),
+            ListenAddress::V4(_) => None,
+        }
+    }
+
+    /// Returns the TCP addresses.
+    pub fn tcp_addresses(&self) -> impl Iterator<Item = Multiaddr> + '_ {
+        let v4_multiaddr = self
+            .v4()
+            .map(|v4_addr| Multiaddr::from(v4_addr.addr).with(Protocol::Tcp(v4_addr.tcp_port)));
+        let v6_multiaddr = self
+            .v6()
+            .map(|v6_addr| Multiaddr::from(v6_addr.addr).with(Protocol::Tcp(v6_addr.tcp_port)));
+        v4_multiaddr.into_iter().chain(v6_multiaddr)
+    }
+
+    #[cfg(test)]
+    pub fn unused_v4_ports() -> Self {
+        ListenAddress::V4(ListenAddr {
+            addr: Ipv4Addr::UNSPECIFIED,
+            udp_port: unused_port::unused_udp4_port().unwrap(),
+            tcp_port: unused_port::unused_tcp4_port().unwrap(),
+        })
+    }
+
+    #[cfg(test)]
+    pub fn unused_v6_ports() -> Self {
+        ListenAddress::V6(ListenAddr {
+            addr: Ipv6Addr::UNSPECIFIED,
+            udp_port: unused_port::unused_udp6_port().unwrap(),
+            tcp_port: unused_port::unused_tcp6_port().unwrap(),
+        })
+    }
+}
+
+impl slog::KV for ListenAddress {
+    fn serialize(
+        &self,
+        _record: &slog::Record,
+        serializer: &mut dyn slog::Serializer,
+    ) -> slog::Result {
+        if let Some(v4_addr) = self.v4() {
+            serializer.emit_arguments("ip4_address", &format_args!("{}", v4_addr.addr))?;
+            serializer.emit_u16("udp4_port", v4_addr.udp_port)?;
+            serializer.emit_u16("tcp4_port", v4_addr.tcp_port)?;
+        }
+        if let Some(v6_addr) = self.v6() {
+            serializer.emit_arguments("ip6_address", &format_args!("{}", v6_addr.addr))?;
+            serializer.emit_u16("udp6_port", v6_addr.udp_port)?;
+            serializer.emit_u16("tcp6_port", v6_addr.tcp_port)?;
+        }
+        slog::Result::Ok(())
+    }
+}
diff --git a/beacon_node/lighthouse_network/src/metrics.rs b/beacon_node/lighthouse_network/src/metrics.rs
index 2ee224d5e..aed68e27f 100644
--- a/beacon_node/lighthouse_network/src/metrics.rs
+++ b/beacon_node/lighthouse_network/src/metrics.rs
@@ -159,7 +159,7 @@ pub fn check_nat() {
     if NAT_OPEN.as_ref().map(|v| v.get()).unwrap_or(0) != 0 {
         return;
     }
-    if ADDRESS_UPDATE_COUNT.as_ref().map(|v| v.get()).unwrap_or(0) == 0
+    if ADDRESS_UPDATE_COUNT.as_ref().map(|v| v.get()).unwrap_or(0) != 0
         || NETWORK_INBOUND_PEERS.as_ref().map(|v| v.get()).unwrap_or(0) != 0_i64
     {
         inc_counter(&NAT_OPEN);
diff --git a/beacon_node/lighthouse_network/src/service/mod.rs b/beacon_node/lighthouse_network/src/service/mod.rs
index 9e45c6ad3..ac8251ea6 100644
--- a/beacon_node/lighthouse_network/src/service/mod.rs
+++ b/beacon_node/lighthouse_network/src/service/mod.rs
@@ -165,8 +165,8 @@ impl<AppReqId: ReqId, TSpec: EthSpec> Network<AppReqId, TSpec> {
             let meta_data = utils::load_or_build_metadata(&config.network_dir, &log);
             let globals = NetworkGlobals::new(
                 enr,
-                config.libp2p_port,
-                config.discovery_port,
+                config.listen_addrs().v4().map(|v4_addr| v4_addr.tcp_port),
+                config.listen_addrs().v6().map(|v6_addr| v6_addr.tcp_port),
                 meta_data,
                 config
                     .trusted_peers
@@ -390,36 +390,26 @@ impl<AppReqId: ReqId, TSpec: EthSpec> Network<AppReqId, TSpec> {
     async fn start(&mut self, config: &crate::NetworkConfig) -> error::Result<()> {
         let enr = self.network_globals.local_enr();
         info!(self.log, "Libp2p Starting"; "peer_id" => %enr.peer_id(), "bandwidth_config" => format!("{}-{}", config.network_load, NetworkLoad::from(config.network_load).name));
-        let discovery_string = if config.disable_discovery {
-            "None".into()
-        } else {
-            config.discovery_port.to_string()
-        };
+        debug!(self.log, "Attempting to open listening ports"; config.listen_addrs(), "discovery_enabled" => !config.disable_discovery);
 
-        debug!(self.log, "Attempting to open listening ports"; "address" => ?config.listen_address, "tcp_port" => config.libp2p_port, "udp_port" => discovery_string);
-
-        let listen_multiaddr = {
-            let mut m = Multiaddr::from(config.listen_address);
-            m.push(MProtocol::Tcp(config.libp2p_port));
-            m
-        };
-
-        match self.swarm.listen_on(listen_multiaddr.clone()) {
-            Ok(_) => {
-                let mut log_address = listen_multiaddr;
-                log_address.push(MProtocol::P2p(enr.peer_id().into()));
-                info!(self.log, "Listening established"; "address" => %log_address);
-            }
-            Err(err) => {
-                crit!(
-                    self.log,
-                    "Unable to listen on libp2p address";
-                    "error" => ?err,
-                    "listen_multiaddr" => %listen_multiaddr,
-                );
-                return Err("Libp2p was unable to listen on the given listen address.".into());
-            }
-        };
+        for listen_multiaddr in config.listen_addrs().tcp_addresses() {
+            match self.swarm.listen_on(listen_multiaddr.clone()) {
+                Ok(_) => {
+                    let mut log_address = listen_multiaddr;
+                    log_address.push(MProtocol::P2p(enr.peer_id().into()));
+                    info!(self.log, "Listening established"; "address" => %log_address);
+                }
+                Err(err) => {
+                    crit!(
+                        self.log,
+                        "Unable to listen on libp2p address";
+                        "error" => ?err,
+                        "listen_multiaddr" => %listen_multiaddr,
+                    );
+                    return Err("Libp2p was unable to listen on the given listen address.".into());
+                }
+            };
+        }
 
         // helper closure for dialing peers
         let mut dial = |mut multiaddr: Multiaddr| {
diff --git a/beacon_node/lighthouse_network/src/types/globals.rs b/beacon_node/lighthouse_network/src/types/globals.rs
index aadd13a23..ee2b300e2 100644
--- a/beacon_node/lighthouse_network/src/types/globals.rs
+++ b/beacon_node/lighthouse_network/src/types/globals.rs
@@ -7,7 +7,6 @@ use crate::EnrExt;
 use crate::{Enr, GossipTopic, Multiaddr, PeerId};
 use parking_lot::RwLock;
 use std::collections::HashSet;
-use std::sync::atomic::{AtomicU16, Ordering};
 use types::EthSpec;
 
 pub struct NetworkGlobals<TSpec: EthSpec> {
@@ -17,10 +16,10 @@ pub struct NetworkGlobals<TSpec: EthSpec> {
     pub peer_id: RwLock<PeerId>,
     /// Listening multiaddrs.
     pub listen_multiaddrs: RwLock<Vec<Multiaddr>>,
-    /// The TCP port that the libp2p service is listening on
-    pub listen_port_tcp: AtomicU16,
-    /// The UDP port that the discovery service is listening on
-    pub listen_port_udp: AtomicU16,
+    /// The TCP port that the libp2p service is listening on over Ipv4.
+    listen_port_tcp4: Option<u16>,
+    /// The TCP port that the libp2p service is listening on over Ipv6.
+    listen_port_tcp6: Option<u16>,
     /// The collection of known peers.
     pub peers: RwLock<PeerDB<TSpec>>,
     // The local meta data of our node.
@@ -36,8 +35,8 @@ pub struct NetworkGlobals<TSpec: EthSpec> {
 impl<TSpec: EthSpec> NetworkGlobals<TSpec> {
     pub fn new(
         enr: Enr,
-        tcp_port: u16,
-        udp_port: u16,
+        listen_port_tcp4: Option<u16>,
+        listen_port_tcp6: Option<u16>,
         local_metadata: MetaData<TSpec>,
         trusted_peers: Vec<PeerId>,
         log: &slog::Logger,
@@ -46,8 +45,8 @@ impl<TSpec: EthSpec> NetworkGlobals<TSpec> {
             local_enr: RwLock::new(enr.clone()),
             peer_id: RwLock::new(enr.peer_id()),
             listen_multiaddrs: RwLock::new(Vec::new()),
-            listen_port_tcp: AtomicU16::new(tcp_port),
-            listen_port_udp: AtomicU16::new(udp_port),
+            listen_port_tcp4,
+            listen_port_tcp6,
             local_metadata: RwLock::new(local_metadata),
             peers: RwLock::new(PeerDB::new(trusted_peers, log)),
             gossipsub_subscriptions: RwLock::new(HashSet::new()),
@@ -73,13 +72,13 @@ impl<TSpec: EthSpec> NetworkGlobals<TSpec> {
     }
 
     /// Returns the libp2p TCP port that this node has been configured to listen on.
-    pub fn listen_port_tcp(&self) -> u16 {
-        self.listen_port_tcp.load(Ordering::Relaxed)
+    pub fn listen_port_tcp4(&self) -> Option<u16> {
+        self.listen_port_tcp4
     }
 
     /// Returns the UDP discovery port that this node has been configured to listen on.
-    pub fn listen_port_udp(&self) -> u16 {
-        self.listen_port_udp.load(Ordering::Relaxed)
+    pub fn listen_port_tcp6(&self) -> Option<u16> {
+        self.listen_port_tcp6
     }
 
     /// Returns the number of libp2p connected peers.
@@ -137,8 +136,8 @@ impl<TSpec: EthSpec> NetworkGlobals<TSpec> {
         let enr = discv5::enr::EnrBuilder::new("v4").build(&enr_key).unwrap();
         NetworkGlobals::new(
             enr,
-            9000,
-            9000,
+            Some(9000),
+            None,
             MetaData::V2(MetaDataV2 {
                 seq_number: 0,
                 attnets: Default::default(),
diff --git a/beacon_node/lighthouse_network/tests/common.rs b/beacon_node/lighthouse_network/tests/common.rs
index 8cc46940b..bd153284e 100644
--- a/beacon_node/lighthouse_network/tests/common.rs
+++ b/beacon_node/lighthouse_network/tests/common.rs
@@ -13,7 +13,7 @@ use tokio::runtime::Runtime;
 use types::{
     ChainSpec, EnrForkId, Epoch, EthSpec, ForkContext, ForkName, Hash256, MinimalEthSpec, Slot,
 };
-use unused_port::unused_tcp_port;
+use unused_port::unused_tcp4_port;
 
 type E = MinimalEthSpec;
 type ReqId = usize;
@@ -78,11 +78,9 @@ pub fn build_config(port: u16, mut boot_nodes: Vec<Enr>) -> NetworkConfig {
         .tempdir()
         .unwrap();
 
-    config.libp2p_port = port; // tcp port
-    config.discovery_port = port; // udp port
-    config.enr_tcp_port = Some(port);
-    config.enr_udp_port = Some(port);
-    config.enr_address = Some("127.0.0.1".parse().unwrap());
+    config.set_ipv4_listening_address(std::net::Ipv4Addr::UNSPECIFIED, port, port);
+    config.enr_udp4_port = Some(port);
+    config.enr_address = (Some(std::net::Ipv4Addr::LOCALHOST), None);
     config.boot_nodes_enr.append(&mut boot_nodes);
     config.network_dir = path.into_path();
     // Reduce gossipsub heartbeat parameters
@@ -100,7 +98,7 @@ pub async fn build_libp2p_instance(
     log: slog::Logger,
     fork_name: ForkName,
 ) -> Libp2pInstance {
-    let port = unused_tcp_port().unwrap();
+    let port = unused_tcp4_port().unwrap();
     let config = build_config(port, boot_nodes);
     // launch libp2p service
 
diff --git a/beacon_node/network/src/beacon_processor/tests.rs b/beacon_node/network/src/beacon_processor/tests.rs
index e2b96fb47..cf4934a66 100644
--- a/beacon_node/network/src/beacon_processor/tests.rs
+++ b/beacon_node/network/src/beacon_processor/tests.rs
@@ -36,7 +36,6 @@ const SMALL_CHAIN: u64 = 2;
 const LONG_CHAIN: u64 = SLOTS_PER_EPOCH * 2;
 
 const TCP_PORT: u16 = 42;
-const UDP_PORT: u16 = 42;
 const SEQ_NUMBER: u64 = 0;
 
 /// The default time to wait for `BeaconProcessor` events.
@@ -177,8 +176,8 @@ impl TestRig {
         let enr = EnrBuilder::new("v4").build(&enr_key).unwrap();
         let network_globals = Arc::new(NetworkGlobals::new(
             enr,
-            TCP_PORT,
-            UDP_PORT,
+            Some(TCP_PORT),
+            None,
             meta_data,
             vec![],
             &log,
diff --git a/beacon_node/network/src/nat.rs b/beacon_node/network/src/nat.rs
index a2fbe5761..9bf123e8d 100644
--- a/beacon_node/network/src/nat.rs
+++ b/beacon_node/network/src/nat.rs
@@ -20,13 +20,13 @@ pub struct UPnPConfig {
     disable_discovery: bool,
 }
 
-impl From<&NetworkConfig> for UPnPConfig {
-    fn from(config: &NetworkConfig) -> Self {
-        UPnPConfig {
-            tcp_port: config.libp2p_port,
-            udp_port: config.discovery_port,
+impl UPnPConfig {
+    pub fn from_config(config: &NetworkConfig) -> Option<Self> {
+        config.listen_addrs().v4().map(|v4_addr| UPnPConfig {
+            tcp_port: v4_addr.tcp_port,
+            udp_port: v4_addr.udp_port,
             disable_discovery: config.disable_discovery,
-        }
+        })
     }
 }
 
diff --git a/beacon_node/network/src/service.rs b/beacon_node/network/src/service.rs
index c3d1ca2a0..9bd68f4e7 100644
--- a/beacon_node/network/src/service.rs
+++ b/beacon_node/network/src/service.rs
@@ -228,16 +228,21 @@ impl<T: BeaconChainTypes> NetworkService<T> {
         let (network_senders, network_recievers) = NetworkSenders::new();
 
         // try and construct UPnP port mappings if required.
-        let upnp_config = crate::nat::UPnPConfig::from(config);
-        let upnp_log = network_log.new(o!("service" => "UPnP"));
-        let upnp_network_send = network_senders.network_send();
-        if config.upnp_enabled {
-            executor.spawn_blocking(
-                move || {
-                    crate::nat::construct_upnp_mappings(upnp_config, upnp_network_send, upnp_log)
-                },
-                "UPnP",
-            );
+        if let Some(upnp_config) = crate::nat::UPnPConfig::from_config(config) {
+            let upnp_log = network_log.new(o!("service" => "UPnP"));
+            let upnp_network_send = network_senders.network_send();
+            if config.upnp_enabled {
+                executor.spawn_blocking(
+                    move || {
+                        crate::nat::construct_upnp_mappings(
+                            upnp_config,
+                            upnp_network_send,
+                            upnp_log,
+                        )
+                    },
+                    "UPnP",
+                );
+            }
         }
 
         // get a reference to the beacon chain store
diff --git a/beacon_node/network/src/service/tests.rs b/beacon_node/network/src/service/tests.rs
index a21424d7d..633b83ddd 100644
--- a/beacon_node/network/src/service/tests.rs
+++ b/beacon_node/network/src/service/tests.rs
@@ -61,10 +61,9 @@ mod tests {
         );
 
         let mut config = NetworkConfig::default();
+        config.set_ipv4_listening_address(std::net::Ipv4Addr::UNSPECIFIED, 21212, 21212);
         config.discv5_config.table_filter = |_| true; // Do not ignore local IPs
-        config.libp2p_port = 21212;
         config.upnp_enabled = false;
-        config.discovery_port = 21212;
         config.boot_nodes_enr = enrs.clone();
         runtime.block_on(async move {
             // Create a new network service which implicitly gets dropped at the
diff --git a/beacon_node/src/cli.rs b/beacon_node/src/cli.rs
index cedb06f8c..d708d145f 100644
--- a/beacon_node/src/cli.rs
+++ b/beacon_node/src/cli.rs
@@ -78,7 +78,16 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
             Arg::with_name("listen-address")
                 .long("listen-address")
                 .value_name("ADDRESS")
-                .help("The address lighthouse will listen for UDP and TCP connections.")
+                .help("The address lighthouse will listen for UDP and TCP connections. To listen \
+                      over IpV4 and IpV6 set this flag twice with the different values.\n\
+                      Examples:\n\
+                      - --listen-address '0.0.0.0' will listen over Ipv4.\n\
+                      - --listen-address '::' will listen over Ipv6.\n\
+                      - --listen-address '0.0.0.0' --listen-address '::' will listen over both \
+                      Ipv4 and Ipv6. The order of the given addresses is not relevant. However, \
+                      multiple Ipv4, or multiple Ipv6 addresses will not be accepted.")
+                .multiple(true)
+                .max_values(2)
                 .default_value("0.0.0.0")
                 .takes_value(true)
         )
@@ -86,10 +95,21 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
             Arg::with_name("port")
                 .long("port")
                 .value_name("PORT")
-                .help("The TCP/UDP port to listen on. The UDP port can be modified by the --discovery-port flag.")
+                .help("The TCP/UDP port to listen on. The UDP port can be modified by the \
+                      --discovery-port flag. If listening over both Ipv4 and Ipv6 the --port flag \
+                      will apply to the Ipv4 address and --port6 to the Ipv6 address.")
                 .default_value("9000")
                 .takes_value(true),
         )
+        .arg(
+            Arg::with_name("port6")
+                .long("port6")
+                .value_name("PORT")
+                .help("The TCP/UDP port to listen on over IpV6 when listening over both Ipv4 and \
+                      Ipv6. Defaults to 9090 when required.")
+                .default_value("9090")
+                .takes_value(true),
+        )
         .arg(
             Arg::with_name("discovery-port")
                 .long("discovery-port")
@@ -97,6 +117,15 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
                 .help("The UDP port that discovery will listen on. Defaults to `port`")
                 .takes_value(true),
         )
+        .arg(
+            Arg::with_name("discovery-port6")
+                .long("discovery-port6")
+                .value_name("PORT")
+                .help("The UDP port that discovery will listen on over IpV6 if listening over \
+                      both Ipv4 and IpV6. Defaults to `port6`")
+                .hidden(true) // TODO: implement dual stack via two sockets in discv5.
+                .takes_value(true),
+        )
         .arg(
             Arg::with_name("target-peers")
                 .long("target-peers")
@@ -137,27 +166,49 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
             Arg::with_name("enr-udp-port")
                 .long("enr-udp-port")
                 .value_name("PORT")
-                .help("The UDP port of the local ENR. Set this only if you are sure other nodes can connect to your local node on this port.")
+                .help("The UDP4 port of the local ENR. Set this only if you are sure other nodes \
+                      can connect to your local node on this port over IpV4.")
+                .takes_value(true),
+        )
+        .arg(
+            Arg::with_name("enr-udp6-port")
+                .long("enr-udp6-port")
+                .value_name("PORT")
+                .help("The UDP6 port of the local ENR. Set this only if you are sure other nodes \
+                      can connect to your local node on this port over IpV6.")
                 .takes_value(true),
         )
         .arg(
             Arg::with_name("enr-tcp-port")
                 .long("enr-tcp-port")
                 .value_name("PORT")
-                .help("The TCP port of the local ENR. Set this only if you are sure other nodes can connect to your local node on this port.\
-                    The --port flag is used if this is not set.")
+                .help("The TCP4 port of the local ENR. Set this only if you are sure other nodes \
+                      can connect to your local node on this port over IpV4. The --port flag is \
+                      used if this is not set.")
+                .takes_value(true),
+        )
+        .arg(
+            Arg::with_name("enr-tcp6-port")
+                .long("enr-tcp6-port")
+                .value_name("PORT")
+                .help("The TCP6 port of the local ENR. Set this only if you are sure other nodes \
+                      can connect to your local node on this port over IpV6. The --port6 flag is \
+                      used if this is not set.")
                 .takes_value(true),
         )
         .arg(
             Arg::with_name("enr-address")
                 .long("enr-address")
                 .value_name("ADDRESS")
-                .help("The IP address/ DNS address to broadcast to other peers on how to reach this node. \
-                If a DNS address is provided, the enr-address is set to the IP address it resolves to and \
-                does not auto-update based on PONG responses in discovery. \
-                Set this only if you are sure other nodes can connect to your local node on this address. \
-                Discovery will automatically find your external address, if possible.")
+                .help("The IP address/ DNS address to broadcast to other peers on how to reach \
+                      this node. If a DNS address is provided, the enr-address is set to the IP \
+                      address it resolves to and does not auto-update based on PONG responses in \
+                      discovery. Set this only if you are sure other nodes can connect to your \
+                      local node on this address. This will update the `ip4` or `ip6` ENR fields \
+                      accordingly. To update both, set this flag twice with the different values.")
                 .requires("enr-udp-port")
+                .multiple(true)
+                .max_values(2)
                 .takes_value(true),
         )
         .arg(
@@ -165,7 +216,8 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
                 .short("e")
                 .long("enr-match")
                 .help("Sets the local ENR IP address and port to match those set for lighthouse. \
-                Specifically, the IP address will be the value of --listen-address and the UDP port will be --discovery-port.")
+                      Specifically, the IP address will be the value of --listen-address and the \
+                      UDP port will be --discovery-port.")
         )
         .arg(
             Arg::with_name("disable-enr-auto-update")
diff --git a/beacon_node/src/config.rs b/beacon_node/src/config.rs
index aa1270487..c0bf83a0f 100644
--- a/beacon_node/src/config.rs
+++ b/beacon_node/src/config.rs
@@ -11,13 +11,13 @@ use environment::RuntimeContext;
 use execution_layer::DEFAULT_JWT_FILE;
 use genesis::Eth1Endpoint;
 use http_api::TlsConfig;
+use lighthouse_network::ListenAddress;
 use lighthouse_network::{multiaddr::Protocol, Enr, Multiaddr, NetworkConfig, PeerIdSerialized};
 use sensitive_url::SensitiveUrl;
 use slog::{info, warn, Logger};
 use std::cmp;
 use std::cmp::max;
 use std::fmt::Debug;
-use std::fmt::Write;
 use std::fs;
 use std::net::Ipv6Addr;
 use std::net::{IpAddr, Ipv4Addr, ToSocketAddrs};
@@ -25,7 +25,6 @@ use std::path::{Path, PathBuf};
 use std::str::FromStr;
 use std::time::Duration;
 use types::{Checkpoint, Epoch, EthSpec, Hash256, PublicKeyBytes, GRAFFITI_BYTES_LEN};
-use unused_port::{unused_tcp_port, unused_udp_port};
 
 /// Gets the fully-initialized global client.
 ///
@@ -79,13 +78,7 @@ pub fn get_config<E: EthSpec>(
 
     let data_dir_ref = client_config.data_dir().clone();
 
-    set_network_config(
-        &mut client_config.network,
-        cli_args,
-        &data_dir_ref,
-        log,
-        false,
-    )?;
+    set_network_config(&mut client_config.network, cli_args, &data_dir_ref, log)?;
 
     /*
      * Staking flag
@@ -441,13 +434,6 @@ pub fn get_config<E: EthSpec>(
      * Discovery address is set to localhost by default.
      */
     if cli_args.is_present("zero-ports") {
-        if client_config.network.enr_address == Some(IpAddr::V4(Ipv4Addr::new(0, 0, 0, 0))) {
-            client_config.network.enr_address = None
-        }
-        client_config.network.libp2p_port =
-            unused_tcp_port().map_err(|e| format!("Failed to get port for libp2p: {}", e))?;
-        client_config.network.discovery_port =
-            unused_udp_port().map_err(|e| format!("Failed to get port for discovery: {}", e))?;
         client_config.http_api.listen_port = 0;
         client_config.http_metrics.listen_port = 0;
     }
@@ -798,13 +784,177 @@ pub fn get_config<E: EthSpec>(
     Ok(client_config)
 }
 
-/// Sets the network config from the command line arguments
+/// Gets the listening_addresses for lighthouse based on the cli options.
+pub fn parse_listening_addresses(
+    cli_args: &ArgMatches,
+    log: &Logger,
+) -> Result<ListenAddress, String> {
+    let listen_addresses_str = cli_args
+        .values_of("listen-address")
+        .expect("--listen_addresses has a default value");
+
+    let use_zero_ports = cli_args.is_present("zero-ports");
+
+    // parse the possible ips
+    let mut maybe_ipv4 = None;
+    let mut maybe_ipv6 = None;
+    for addr_str in listen_addresses_str {
+        let addr = addr_str.parse::<IpAddr>().map_err(|parse_error| {
+            format!("Failed to parse listen-address ({addr_str}) as an Ip address: {parse_error}")
+        })?;
+
+        match addr {
+            IpAddr::V4(v4_addr) => match &maybe_ipv4 {
+                Some(first_ipv4_addr) => {
+                    return Err(format!(
+                                "When setting the --listen-address option twice, use an IpV4 address and an Ipv6 address. \
+                                Got two IpV4 addresses {first_ipv4_addr} and {v4_addr}"
+                            ));
+                }
+                None => maybe_ipv4 = Some(v4_addr),
+            },
+            IpAddr::V6(v6_addr) => match &maybe_ipv6 {
+                Some(first_ipv6_addr) => {
+                    return Err(format!(
+                                "When setting the --listen-address option twice, use an IpV4 address and an Ipv6 address. \
+                                Got two IpV6 addresses {first_ipv6_addr} and {v6_addr}"
+                            ));
+                }
+                None => maybe_ipv6 = Some(v6_addr),
+            },
+        }
+    }
+
+    // parse the possible tcp ports
+    let port = cli_args
+        .value_of("port")
+        .expect("--port has a default value")
+        .parse::<u16>()
+        .map_err(|parse_error| format!("Failed to parse --port as an integer: {parse_error}"))?;
+    let port6 = cli_args
+        .value_of("port6")
+        .map(str::parse::<u16>)
+        .transpose()
+        .map_err(|parse_error| format!("Failed to parse --port6 as an integer: {parse_error}"))?
+        .unwrap_or(9090);
+
+    // parse the possible udp ports
+    let maybe_udp_port = cli_args
+        .value_of("discovery-port")
+        .map(str::parse::<u16>)
+        .transpose()
+        .map_err(|parse_error| {
+            format!("Failed to parse --discovery-port as an integer: {parse_error}")
+        })?;
+    let maybe_udp6_port = cli_args
+        .value_of("discovery-port6")
+        .map(str::parse::<u16>)
+        .transpose()
+        .map_err(|parse_error| {
+            format!("Failed to parse --discovery-port6 as an integer: {parse_error}")
+        })?;
+
+    // Now put everything together
+    let listening_addresses = match (maybe_ipv4, maybe_ipv6) {
+        (None, None) => {
+            // This should never happen unless clap is broken
+            return Err("No listening addresses provided".into());
+        }
+        (None, Some(ipv6)) => {
+            // A single ipv6 address was provided. Set the ports
+
+            if cli_args.is_present("port6") {
+                warn!(log, "When listening only over IpV6, use the --port flag. The value of --port6 will be ignored.")
+            }
+            // use zero ports if required. If not, use the given port.
+            let tcp_port = use_zero_ports
+                .then(unused_port::unused_tcp6_port)
+                .transpose()?
+                .unwrap_or(port);
+
+            if maybe_udp6_port.is_some() {
+                warn!(log, "When listening only over IpV6, use the --discovery-port flag. The value of --discovery-port6 will be ignored.")
+            }
+            // use zero ports if required. If not, use the specific udp port. If none given, use
+            // the tcp port.
+            let udp_port = use_zero_ports
+                .then(unused_port::unused_udp6_port)
+                .transpose()?
+                .or(maybe_udp_port)
+                .unwrap_or(port);
+
+            ListenAddress::V6(lighthouse_network::ListenAddr {
+                addr: ipv6,
+                udp_port,
+                tcp_port,
+            })
+        }
+        (Some(ipv4), None) => {
+            // A single ipv4 address was provided. Set the ports
+
+            // use zero ports if required. If not, use the given port.
+            let tcp_port = use_zero_ports
+                .then(unused_port::unused_tcp4_port)
+                .transpose()?
+                .unwrap_or(port);
+            // use zero ports if required. If not, use the specific udp port. If none given, use
+            // the tcp port.
+            let udp_port = use_zero_ports
+                .then(unused_port::unused_udp4_port)
+                .transpose()?
+                .or(maybe_udp_port)
+                .unwrap_or(port);
+            ListenAddress::V4(lighthouse_network::ListenAddr {
+                addr: ipv4,
+                udp_port,
+                tcp_port,
+            })
+        }
+        (Some(ipv4), Some(ipv6)) => {
+            let ipv4_tcp_port = use_zero_ports
+                .then(unused_port::unused_tcp4_port)
+                .transpose()?
+                .unwrap_or(port);
+            let ipv4_udp_port = use_zero_ports
+                .then(unused_port::unused_udp4_port)
+                .transpose()?
+                .or(maybe_udp_port)
+                .unwrap_or(ipv4_tcp_port);
+
+            // Defaults to 9090 when required
+            let ipv6_tcp_port = use_zero_ports
+                .then(unused_port::unused_tcp6_port)
+                .transpose()?
+                .unwrap_or(port6);
+            let ipv6_udp_port = use_zero_ports
+                .then(unused_port::unused_udp6_port)
+                .transpose()?
+                .or(maybe_udp6_port)
+                .unwrap_or(ipv6_tcp_port);
+            ListenAddress::DualStack(
+                lighthouse_network::ListenAddr {
+                    addr: ipv4,
+                    udp_port: ipv4_udp_port,
+                    tcp_port: ipv4_tcp_port,
+                },
+                lighthouse_network::ListenAddr {
+                    addr: ipv6,
+                    udp_port: ipv6_udp_port,
+                    tcp_port: ipv6_tcp_port,
+                },
+            )
+        }
+    };
+
+    Ok(listening_addresses)
+}
+
+/// Sets the network config from the command line arguments.
 pub fn set_network_config(
     config: &mut NetworkConfig,
     cli_args: &ArgMatches,
     data_dir: &Path,
     log: &Logger,
-    use_listening_port_as_enr_port_by_default: bool,
 ) -> Result<(), String> {
     // If a network dir has been specified, override the `datadir` definition.
     if let Some(dir) = cli_args.value_of("network-dir") {
@@ -825,12 +975,7 @@ pub fn set_network_config(
         config.shutdown_after_sync = true;
     }
 
-    if let Some(listen_address_str) = cli_args.value_of("listen-address") {
-        let listen_address = listen_address_str
-            .parse()
-            .map_err(|_| format!("Invalid listen address: {:?}", listen_address_str))?;
-        config.listen_address = listen_address;
-    }
+    config.set_listening_addr(parse_listening_addresses(cli_args, log)?);
 
     if let Some(target_peers_str) = cli_args.value_of("target-peers") {
         config.target_peers = target_peers_str
@@ -838,21 +983,6 @@ pub fn set_network_config(
             .map_err(|_| format!("Invalid number of target peers: {}", target_peers_str))?;
     }
 
-    if let Some(port_str) = cli_args.value_of("port") {
-        let port = port_str
-            .parse::<u16>()
-            .map_err(|_| format!("Invalid port: {}", port_str))?;
-        config.libp2p_port = port;
-        config.discovery_port = port;
-    }
-
-    if let Some(port_str) = cli_args.value_of("discovery-port") {
-        let port = port_str
-            .parse::<u16>()
-            .map_err(|_| format!("Invalid port: {}", port_str))?;
-        config.discovery_port = port;
-    }
-
     if let Some(value) = cli_args.value_of("network-load") {
         let network_load = value
             .parse::<u8>()
@@ -908,7 +1038,7 @@ pub fn set_network_config(
     }
 
     if let Some(enr_udp_port_str) = cli_args.value_of("enr-udp-port") {
-        config.enr_udp_port = Some(
+        config.enr_udp4_port = Some(
             enr_udp_port_str
                 .parse::<u16>()
                 .map_err(|_| format!("Invalid discovery port: {}", enr_udp_port_str))?,
@@ -916,7 +1046,23 @@ pub fn set_network_config(
     }
 
     if let Some(enr_tcp_port_str) = cli_args.value_of("enr-tcp-port") {
-        config.enr_tcp_port = Some(
+        config.enr_tcp4_port = Some(
+            enr_tcp_port_str
+                .parse::<u16>()
+                .map_err(|_| format!("Invalid ENR TCP port: {}", enr_tcp_port_str))?,
+        );
+    }
+
+    if let Some(enr_udp_port_str) = cli_args.value_of("enr-udp6-port") {
+        config.enr_udp6_port = Some(
+            enr_udp_port_str
+                .parse::<u16>()
+                .map_err(|_| format!("Invalid discovery port: {}", enr_udp_port_str))?,
+        );
+    }
+
+    if let Some(enr_tcp_port_str) = cli_args.value_of("enr-tcp6-port") {
+        config.enr_tcp6_port = Some(
             enr_tcp_port_str
                 .parse::<u16>()
                 .map_err(|_| format!("Invalid ENR TCP port: {}", enr_tcp_port_str))?,
@@ -924,58 +1070,106 @@ pub fn set_network_config(
     }
 
     if cli_args.is_present("enr-match") {
+        // Match the Ip and UDP port in the enr.
+
         // set the enr address to localhost if the address is unspecified
-        if config.listen_address == IpAddr::V4(Ipv4Addr::UNSPECIFIED) {
-            config.enr_address = Some(IpAddr::V4(Ipv4Addr::LOCALHOST));
-        } else if config.listen_address == IpAddr::V6(Ipv6Addr::UNSPECIFIED) {
-            config.enr_address = Some(IpAddr::V6(Ipv6Addr::LOCALHOST));
-        } else {
-            config.enr_address = Some(config.listen_address);
+        if let Some(ipv4_addr) = config.listen_addrs().v4().cloned() {
+            let ipv4_enr_addr = if ipv4_addr.addr == Ipv4Addr::UNSPECIFIED {
+                Ipv4Addr::LOCALHOST
+            } else {
+                ipv4_addr.addr
+            };
+            config.enr_address.0 = Some(ipv4_enr_addr);
+            config.enr_udp4_port = Some(ipv4_addr.udp_port);
+        }
+
+        if let Some(ipv6_addr) = config.listen_addrs().v6().cloned() {
+            let ipv6_enr_addr = if ipv6_addr.addr == Ipv6Addr::UNSPECIFIED {
+                Ipv6Addr::LOCALHOST
+            } else {
+                ipv6_addr.addr
+            };
+            config.enr_address.1 = Some(ipv6_enr_addr);
+            config.enr_udp6_port = Some(ipv6_addr.udp_port);
         }
-        config.enr_udp_port = Some(config.discovery_port);
     }
 
-    if let Some(enr_address) = cli_args.value_of("enr-address") {
-        let resolved_addr = match enr_address.parse::<IpAddr>() {
-            Ok(addr) => addr, // // Input is an IpAddr
-            Err(_) => {
-                let mut addr = enr_address.to_string();
-                // Appending enr-port to the dns hostname to appease `to_socket_addrs()` parsing.
-                // Since enr-update is disabled with a dns address, not setting the enr-udp-port
-                // will make the node undiscoverable.
-                if let Some(enr_udp_port) =
-                    config
-                        .enr_udp_port
-                        .or(if use_listening_port_as_enr_port_by_default {
-                            Some(config.discovery_port)
-                        } else {
-                            None
-                        })
-                {
-                    write!(addr, ":{}", enr_udp_port)
-                        .map_err(|e| format!("Failed to write enr address {}", e))?;
-                } else {
-                    return Err(
-                        "enr-udp-port must be set for node to be discoverable with dns address"
-                            .into(),
-                    );
+    if let Some(enr_addresses) = cli_args.values_of("enr-address") {
+        let mut enr_ip4 = None;
+        let mut enr_ip6 = None;
+        let mut resolved_enr_ip4 = None;
+        let mut resolved_enr_ip6 = None;
+
+        for addr in enr_addresses {
+            match addr.parse::<IpAddr>() {
+                Ok(IpAddr::V4(v4_addr)) => {
+                    if let Some(used) = enr_ip4.as_ref() {
+                        warn!(log, "More than one Ipv4 ENR address provided"; "used" => %used, "ignored" => %v4_addr)
+                    } else {
+                        enr_ip4 = Some(v4_addr)
+                    }
+                }
+                Ok(IpAddr::V6(v6_addr)) => {
+                    if let Some(used) = enr_ip6.as_ref() {
+                        warn!(log, "More than one Ipv6 ENR address provided"; "used" => %used, "ignored" => %v6_addr)
+                    } else {
+                        enr_ip6 = Some(v6_addr)
+                    }
+                }
+                Err(_) => {
+                    // Try to resolve the address
+
+                    // NOTE: From checking the `to_socket_addrs` code I don't think the port
+                    // actually matters. Just use the udp port.
+
+                    let port = match config.listen_addrs() {
+                        ListenAddress::V4(v4_addr) => v4_addr.udp_port,
+                        ListenAddress::V6(v6_addr) => v6_addr.udp_port,
+                        ListenAddress::DualStack(v4_addr, _v6_addr) => {
+                            // NOTE: slight preference for ipv4 that I don't think is of importance.
+                            v4_addr.udp_port
+                        }
+                    };
+
+                    let addr_str = format!("{addr}:{port}");
+                    match addr_str.to_socket_addrs() {
+                        Err(_e) => {
+                            return Err(format!("Failed to parse or resolve address {addr}."))
+                        }
+                        Ok(resolved_addresses) => {
+                            for socket_addr in resolved_addresses {
+                                // Use the first ipv4 and first ipv6 addresses present.
+
+                                // NOTE: this means that if two dns addresses are provided, we
+                                // might end up using the ipv4 and ipv6 resolved addresses of just
+                                // the first.
+                                match socket_addr.ip() {
+                                    IpAddr::V4(v4_addr) => {
+                                        if resolved_enr_ip4.is_none() {
+                                            resolved_enr_ip4 = Some(v4_addr)
+                                        }
+                                    }
+                                    IpAddr::V6(v6_addr) => {
+                                        if resolved_enr_ip6.is_none() {
+                                            resolved_enr_ip6 = Some(v6_addr)
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
                 }
-                // `to_socket_addr()` does the dns resolution
-                // Note: `to_socket_addrs()` is a blocking call
-                let resolved_addr = if let Ok(mut resolved_addrs) = addr.to_socket_addrs() {
-                    // Pick the first ip from the list of resolved addresses
-                    resolved_addrs
-                        .next()
-                        .map(|a| a.ip())
-                        .ok_or("Resolved dns addr contains no entries")?
-                } else {
-                    return Err(format!("Failed to parse enr-address: {}", enr_address));
-                };
-                config.discv5_config.enr_update = false;
-                resolved_addr
             }
-        };
-        config.enr_address = Some(resolved_addr);
+        }
+
+        // The ENR addresses given as ips should take preference over any resolved address
+        let used_host_resolution = resolved_enr_ip4.is_some() || resolved_enr_ip6.is_some();
+        let ip4 = enr_ip4.or(resolved_enr_ip4);
+        let ip6 = enr_ip6.or(resolved_enr_ip6);
+        config.enr_address = (ip4, ip6);
+        if used_host_resolution {
+            config.discv5_config.enr_update = false;
+        }
     }
 
     if cli_args.is_present("disable-enr-auto-update") {
diff --git a/beacon_node/tests/test.rs b/beacon_node/tests/test.rs
index 8ccb260d2..bbec70330 100644
--- a/beacon_node/tests/test.rs
+++ b/beacon_node/tests/test.rs
@@ -1,5 +1,4 @@
 #![cfg(test)]
-#![recursion_limit = "512"]
 
 use beacon_chain::StateSkipConfig;
 use node_test_rig::{
diff --git a/boot_node/src/cli.rs b/boot_node/src/cli.rs
index 9a3732002..c3d7ac48a 100644
--- a/boot_node/src/cli.rs
+++ b/boot_node/src/cli.rs
@@ -53,6 +53,14 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
                 .takes_value(true)
                 .conflicts_with("network-dir")
         )
+        .arg(
+            Arg::with_name("enr-udp6-port")
+                .long("enr-udp6-port")
+                .value_name("PORT")
+                .help("The UDP6 port of the local ENR. Set this only if you are sure other nodes \
+                      can connect to your local node on this port over IpV6.")
+                .takes_value(true),
+        )
         .arg(
             Arg::with_name("enable-enr-auto-update")
                 .short("x")
diff --git a/boot_node/src/config.rs b/boot_node/src/config.rs
index b7a66cbbd..d3ee58a90 100644
--- a/boot_node/src/config.rs
+++ b/boot_node/src/config.rs
@@ -1,7 +1,7 @@
 use beacon_node::{get_data_dir, set_network_config};
 use clap::ArgMatches;
 use eth2_network_config::Eth2NetworkConfig;
-use lighthouse_network::discv5::enr::EnrBuilder;
+use lighthouse_network::discovery::create_enr_builder_from_config;
 use lighthouse_network::discv5::IpMode;
 use lighthouse_network::discv5::{enr::CombinedKey, Discv5Config, Enr};
 use lighthouse_network::{
@@ -57,12 +57,24 @@ impl<T: EthSpec> BootNodeConfig<T> {
 
         let logger = slog_scope::logger();
 
-        set_network_config(&mut network_config, matches, &data_dir, &logger, true)?;
+        set_network_config(&mut network_config, matches, &data_dir, &logger)?;
 
-        // Set the enr-udp-port to the default listening port if it was not specified.
-        if !matches.is_present("enr-udp-port") {
-            network_config.enr_udp_port = Some(network_config.discovery_port);
-        }
+        // Set the Enr UDP ports to the listening ports if not present.
+        if let Some(listening_addr_v4) = network_config.listen_addrs().v4() {
+            network_config.enr_udp4_port = Some(
+                network_config
+                    .enr_udp4_port
+                    .unwrap_or(listening_addr_v4.udp_port),
+            )
+        };
+
+        if let Some(listening_addr_v6) = network_config.listen_addrs().v6() {
+            network_config.enr_udp6_port = Some(
+                network_config
+                    .enr_udp6_port
+                    .unwrap_or(listening_addr_v6.udp_port),
+            )
+        };
 
         // By default this is enabled. If it is not set, revert to false.
         if !matches.is_present("enable-enr-auto-update") {
@@ -70,17 +82,29 @@ impl<T: EthSpec> BootNodeConfig<T> {
         }
 
         // the address to listen on
-        let listen_socket =
-            SocketAddr::new(network_config.listen_address, network_config.discovery_port);
-        if listen_socket.is_ipv6() {
-            // create ipv6 sockets and enable ipv4 mapped addresses.
-            network_config.discv5_config.ip_mode = IpMode::Ip6 {
-                enable_mapped_addresses: true,
-            };
-        } else {
-            // Set explicitly as ipv4 otherwise
-            network_config.discv5_config.ip_mode = IpMode::Ip4;
-        }
+        let listen_socket = match network_config.listen_addrs().clone() {
+            lighthouse_network::ListenAddress::V4(v4_addr) => {
+                // Set explicitly as ipv4 otherwise
+                network_config.discv5_config.ip_mode = IpMode::Ip4;
+                v4_addr.udp_socket_addr()
+            }
+            lighthouse_network::ListenAddress::V6(v6_addr) => {
+                // create ipv6 sockets and enable ipv4 mapped addresses.
+                network_config.discv5_config.ip_mode = IpMode::Ip6 {
+                    enable_mapped_addresses: false,
+                };
+
+                v6_addr.udp_socket_addr()
+            }
+            lighthouse_network::ListenAddress::DualStack(_v4_addr, v6_addr) => {
+                // create ipv6 sockets and enable ipv4 mapped addresses.
+                network_config.discv5_config.ip_mode = IpMode::Ip6 {
+                    enable_mapped_addresses: true,
+                };
+
+                v6_addr.udp_socket_addr()
+            }
+        };
 
         let private_key = load_private_key(&network_config, &logger);
         let local_key = CombinedKey::from_libp2p(&private_key)?;
@@ -115,30 +139,8 @@ impl<T: EthSpec> BootNodeConfig<T> {
             // Build the local ENR
 
             let mut local_enr = {
-                let mut builder = EnrBuilder::new("v4");
-                // Set the enr address if specified. Set also the port.
-                // NOTE: if the port is specified but the the address is not, the port won't be
-                // set since it can't be known if it's an ipv6 or ipv4 udp port.
-                if let Some(enr_address) = network_config.enr_address {
-                    match enr_address {
-                        std::net::IpAddr::V4(ipv4_addr) => {
-                            builder.ip4(ipv4_addr);
-                            if let Some(port) = network_config.enr_udp_port {
-                                builder.udp4(port);
-                            }
-                        }
-                        std::net::IpAddr::V6(ipv6_addr) => {
-                            builder.ip6(ipv6_addr);
-                            if let Some(port) = network_config.enr_udp_port {
-                                builder.udp6(port);
-                                // We are enabling mapped addresses in the boot node in this case,
-                                // so advertise an udp4 port as well.
-                                builder.udp4(port);
-                            }
-                        }
-                    }
-                };
-
+                let enable_tcp = false;
+                let mut builder = create_enr_builder_from_config(&network_config, enable_tcp);
                 // If we know of the ENR field, add it to the initial construction
                 if let Some(enr_fork_bytes) = enr_fork {
                     builder.add_value("eth2", enr_fork_bytes.as_slice());
diff --git a/common/compare_fields_derive/src/lib.rs b/common/compare_fields_derive/src/lib.rs
index 752c09ee0..a8b92b3d5 100644
--- a/common/compare_fields_derive/src/lib.rs
+++ b/common/compare_fields_derive/src/lib.rs
@@ -1,4 +1,3 @@
-#![recursion_limit = "256"]
 extern crate proc_macro;
 
 use proc_macro::TokenStream;
diff --git a/common/eth2/src/types.rs b/common/eth2/src/types.rs
index d6db3e15f..40512d9a5 100644
--- a/common/eth2/src/types.rs
+++ b/common/eth2/src/types.rs
@@ -921,6 +921,8 @@ pub struct SseExtendedPayloadAttributesGeneric<T> {
     #[serde(with = "eth2_serde_utils::quoted_u64")]
     pub proposer_index: u64,
     pub parent_block_root: Hash256,
+    #[serde(with = "eth2_serde_utils::quoted_u64")]
+    pub parent_block_number: u64,
     pub parent_block_hash: ExecutionBlockHash,
     pub payload_attributes: T,
 }
@@ -958,6 +960,7 @@ impl ForkVersionDeserialize for SseExtendedPayloadAttributes {
             proposal_slot: helper.proposal_slot,
             proposer_index: helper.proposer_index,
             parent_block_root: helper.parent_block_root,
+            parent_block_number: helper.parent_block_number,
             parent_block_hash: helper.parent_block_hash,
             payload_attributes: SsePayloadAttributes::deserialize_by_fork::<D>(
                 helper.payload_attributes,
diff --git a/common/unused_port/src/lib.rs b/common/unused_port/src/lib.rs
index 4a8cf1738..a5d081721 100644
--- a/common/unused_port/src/lib.rs
+++ b/common/unused_port/src/lib.rs
@@ -6,14 +6,30 @@ pub enum Transport {
     Udp,
 }
 
-/// A convenience function for `unused_port(Transport::Tcp)`.
-pub fn unused_tcp_port() -> Result<u16, String> {
-    unused_port(Transport::Tcp)
+#[derive(Copy, Clone)]
+pub enum IpVersion {
+    Ipv4,
+    Ipv6,
 }
 
-/// A convenience function for `unused_port(Transport::Tcp)`.
-pub fn unused_udp_port() -> Result<u16, String> {
-    unused_port(Transport::Udp)
+/// A convenience wrapper over [`zero_port`].
+pub fn unused_tcp4_port() -> Result<u16, String> {
+    zero_port(Transport::Tcp, IpVersion::Ipv4)
+}
+
+/// A convenience wrapper over [`zero_port`].
+pub fn unused_udp4_port() -> Result<u16, String> {
+    zero_port(Transport::Udp, IpVersion::Ipv4)
+}
+
+/// A convenience wrapper over [`zero_port`].
+pub fn unused_tcp6_port() -> Result<u16, String> {
+    zero_port(Transport::Tcp, IpVersion::Ipv6)
+}
+
+/// A convenience wrapper over [`zero_port`].
+pub fn unused_udp6_port() -> Result<u16, String> {
+    zero_port(Transport::Udp, IpVersion::Ipv6)
 }
 
 /// A bit of hack to find an unused port.
@@ -26,10 +42,15 @@ pub fn unused_udp_port() -> Result<u16, String> {
 /// It is possible that users are unable to bind to the ports returned by this function as the OS
 /// has a buffer period where it doesn't allow binding to the same port even after the socket is
 /// closed. We might have to use SO_REUSEADDR socket option from `std::net2` crate in that case.
-pub fn unused_port(transport: Transport) -> Result<u16, String> {
+pub fn zero_port(transport: Transport, ipv: IpVersion) -> Result<u16, String> {
+    let localhost = match ipv {
+        IpVersion::Ipv4 => std::net::Ipv4Addr::LOCALHOST.into(),
+        IpVersion::Ipv6 => std::net::Ipv6Addr::LOCALHOST.into(),
+    };
+    let socket_addr = std::net::SocketAddr::new(localhost, 0);
     let local_addr = match transport {
         Transport::Tcp => {
-            let listener = TcpListener::bind("127.0.0.1:0").map_err(|e| {
+            let listener = TcpListener::bind(socket_addr).map_err(|e| {
                 format!("Failed to create TCP listener to find unused port: {:?}", e)
             })?;
             listener.local_addr().map_err(|e| {
@@ -40,7 +61,7 @@ pub fn unused_port(transport: Transport) -> Result<u16, String> {
             })?
         }
         Transport::Udp => {
-            let socket = UdpSocket::bind("127.0.0.1:0")
+            let socket = UdpSocket::bind(socket_addr)
                 .map_err(|e| format!("Failed to create UDP socket to find unused port: {:?}", e))?;
             socket.local_addr().map_err(|e| {
                 format!(
diff --git a/common/warp_utils/src/lib.rs b/common/warp_utils/src/lib.rs
index 346361b18..77d61251f 100644
--- a/common/warp_utils/src/lib.rs
+++ b/common/warp_utils/src/lib.rs
@@ -6,3 +6,4 @@ pub mod metrics;
 pub mod query;
 pub mod reject;
 pub mod task;
+pub mod uor;
diff --git a/common/warp_utils/src/task.rs b/common/warp_utils/src/task.rs
index c3b3e86e2..001231f2c 100644
--- a/common/warp_utils/src/task.rs
+++ b/common/warp_utils/src/task.rs
@@ -1,4 +1,5 @@
 use serde::Serialize;
+use warp::reply::{Reply, Response};
 
 /// A convenience wrapper around `blocking_task`.
 pub async fn blocking_task<F, T>(func: F) -> Result<T, warp::Rejection>
@@ -8,16 +9,29 @@ where
 {
     tokio::task::spawn_blocking(func)
         .await
-        .unwrap_or_else(|_| Err(warp::reject::reject())) // This should really be a 500
+        .unwrap_or_else(|_| Err(warp::reject::reject()))
+}
+
+/// A convenience wrapper around `blocking_task` that returns a `warp::reply::Response`.
+///
+/// Using this method consistently makes it possible to simplify types using `.unify()` or `.uor()`.
+pub async fn blocking_response_task<F, T>(func: F) -> Result<Response, warp::Rejection>
+where
+    F: FnOnce() -> Result<T, warp::Rejection> + Send + 'static,
+    T: Reply + Send + 'static,
+{
+    blocking_task(func).await.map(Reply::into_response)
 }
 
 /// A convenience wrapper around `blocking_task` for use with `warp` JSON responses.
-pub async fn blocking_json_task<F, T>(func: F) -> Result<warp::reply::Json, warp::Rejection>
+pub async fn blocking_json_task<F, T>(func: F) -> Result<Response, warp::Rejection>
 where
     F: FnOnce() -> Result<T, warp::Rejection> + Send + 'static,
     T: Serialize + Send + 'static,
 {
-    blocking_task(func)
-        .await
-        .map(|resp| warp::reply::json(&resp))
+    blocking_response_task(|| {
+        let response = func()?;
+        Ok(warp::reply::json(&response))
+    })
+    .await
 }
diff --git a/common/warp_utils/src/uor.rs b/common/warp_utils/src/uor.rs
new file mode 100644
index 000000000..363f1df7d
--- /dev/null
+++ b/common/warp_utils/src/uor.rs
@@ -0,0 +1,25 @@
+use warp::{filters::BoxedFilter, Filter, Rejection};
+
+/// Mixin trait for `Filter` providing the unifying-or method.
+pub trait UnifyingOrFilter: Filter<Error = Rejection> + Sized + Send + Sync + 'static
+where
+    Self::Extract: Send,
+{
+    /// Unifying `or`.
+    ///
+    /// This is a shorthand for `self.or(other).unify().boxed()`, which is useful because it keeps
+    /// the filter type simple and prevents type-checker explosions.
+    fn uor<F>(self, other: F) -> BoxedFilter<Self::Extract>
+    where
+        F: Filter<Extract = Self::Extract, Error = Rejection> + Clone + Send + Sync + 'static,
+    {
+        self.or(other).unify().boxed()
+    }
+}
+
+impl<F> UnifyingOrFilter for F
+where
+    F: Filter<Error = Rejection> + Sized + Send + Sync + 'static,
+    F::Extract: Send,
+{
+}
diff --git a/consensus/ssz_derive/src/lib.rs b/consensus/ssz_derive/src/lib.rs
index 9f8270e6d..a5c4b7bb6 100644
--- a/consensus/ssz_derive/src/lib.rs
+++ b/consensus/ssz_derive/src/lib.rs
@@ -1,4 +1,3 @@
-#![recursion_limit = "256"]
 //! Provides procedural derive macros for the `Encode` and `Decode` traits of the `eth2_ssz` crate.
 //!
 //! ## Attributes
diff --git a/consensus/tree_hash_derive/src/lib.rs b/consensus/tree_hash_derive/src/lib.rs
index 21ff324d5..85ece80fb 100644
--- a/consensus/tree_hash_derive/src/lib.rs
+++ b/consensus/tree_hash_derive/src/lib.rs
@@ -1,4 +1,3 @@
-#![recursion_limit = "256"]
 use darling::FromDeriveInput;
 use proc_macro::TokenStream;
 use quote::quote;
diff --git a/consensus/types/src/lib.rs b/consensus/types/src/lib.rs
index 380f5e527..221dda31b 100644
--- a/consensus/types/src/lib.rs
+++ b/consensus/types/src/lib.rs
@@ -1,6 +1,4 @@
 //! Ethereum 2.0 types
-// Required for big type-level numbers
-#![recursion_limit = "128"]
 // Clippy lint set up
 #![cfg_attr(
     not(test),
diff --git a/lcli/src/generate_bootnode_enr.rs b/lcli/src/generate_bootnode_enr.rs
index 6f39392d1..8662a8047 100644
--- a/lcli/src/generate_bootnode_enr.rs
+++ b/lcli/src/generate_bootnode_enr.rs
@@ -3,15 +3,14 @@ use lighthouse_network::{
     discovery::{build_enr, CombinedKey, CombinedKeyExt, Keypair, ENR_FILENAME},
     NetworkConfig, NETWORK_KEY_FILENAME,
 };
-use std::fs;
 use std::fs::File;
 use std::io::Write;
-use std::net::IpAddr;
 use std::path::PathBuf;
+use std::{fs, net::Ipv4Addr};
 use types::{ChainSpec, EnrForkId, Epoch, EthSpec, Hash256};
 
 pub fn run<T: EthSpec>(matches: &ArgMatches) -> Result<(), String> {
-    let ip: IpAddr = clap_utils::parse_required(matches, "ip")?;
+    let ip: Ipv4Addr = clap_utils::parse_required(matches, "ip")?;
     let udp_port: u16 = clap_utils::parse_required(matches, "udp-port")?;
     let tcp_port: u16 = clap_utils::parse_required(matches, "tcp-port")?;
     let output_dir: PathBuf = clap_utils::parse_required(matches, "output-dir")?;
@@ -25,12 +24,10 @@ pub fn run<T: EthSpec>(matches: &ArgMatches) -> Result<(), String> {
         ));
     }
 
-    let config = NetworkConfig {
-        enr_address: Some(ip),
-        enr_udp_port: Some(udp_port),
-        enr_tcp_port: Some(tcp_port),
-        ..Default::default()
-    };
+    let mut config = NetworkConfig::default();
+    config.enr_address = (Some(ip), None);
+    config.enr_udp4_port = Some(udp_port);
+    config.enr_tcp6_port = Some(tcp_port);
 
     let local_keypair = Keypair::generate_secp256k1();
     let enr_key = CombinedKey::from_libp2p(&local_keypair)?;
diff --git a/lighthouse/src/main.rs b/lighthouse/src/main.rs
index d9ad22dec..b05e78fe5 100644
--- a/lighthouse/src/main.rs
+++ b/lighthouse/src/main.rs
@@ -1,5 +1,3 @@
-#![recursion_limit = "512"]
-
 mod metrics;
 
 use beacon_node::ProductionBeaconNode;
diff --git a/lighthouse/tests/beacon_node.rs b/lighthouse/tests/beacon_node.rs
index c6990ba3d..7f7aca120 100644
--- a/lighthouse/tests/beacon_node.rs
+++ b/lighthouse/tests/beacon_node.rs
@@ -8,7 +8,7 @@ use eth1::Eth1Endpoint;
 use lighthouse_network::PeerId;
 use std::fs::File;
 use std::io::{Read, Write};
-use std::net::IpAddr;
+use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
 use std::path::PathBuf;
 use std::process::Command;
 use std::str::FromStr;
@@ -16,7 +16,7 @@ use std::string::ToString;
 use std::time::Duration;
 use tempfile::TempDir;
 use types::{Address, Checkpoint, Epoch, ExecutionBlockHash, ForkName, Hash256, MainnetEthSpec};
-use unused_port::{unused_tcp_port, unused_udp_port};
+use unused_port::{unused_tcp4_port, unused_tcp6_port, unused_udp4_port, unused_udp6_port};
 
 const DEFAULT_ETH1_ENDPOINT: &str = "http://localhost:8545/";
 
@@ -851,37 +851,188 @@ fn network_shutdown_after_sync_disabled_flag() {
         .with_config(|config| assert!(!config.network.shutdown_after_sync));
 }
 #[test]
-fn network_listen_address_flag() {
-    let addr = "127.0.0.2".parse::<IpAddr>().unwrap();
+fn network_listen_address_flag_v4() {
+    let addr = "127.0.0.2".parse::<Ipv4Addr>().unwrap();
     CommandLineTest::new()
         .flag("listen-address", Some("127.0.0.2"))
         .run_with_zero_port()
-        .with_config(|config| assert_eq!(config.network.listen_address, addr));
+        .with_config(|config| {
+            assert_eq!(
+                config.network.listen_addrs().v4().map(|addr| addr.addr),
+                Some(addr)
+            )
+        });
 }
 #[test]
-fn network_port_flag() {
-    let port = unused_tcp_port().expect("Unable to find unused port.");
+fn network_listen_address_flag_v6() {
+    const ADDR: &str = "::1";
+    let addr = ADDR.parse::<Ipv6Addr>().unwrap();
+    CommandLineTest::new()
+        .flag("listen-address", Some(ADDR))
+        .run_with_zero_port()
+        .with_config(|config| {
+            assert_eq!(
+                config.network.listen_addrs().v6().map(|addr| addr.addr),
+                Some(addr)
+            )
+        });
+}
+#[test]
+fn network_listen_address_flag_dual_stack() {
+    const V4_ADDR: &str = "127.0.0.1";
+    const V6_ADDR: &str = "::1";
+    let ipv6_addr = V6_ADDR.parse::<Ipv6Addr>().unwrap();
+    let ipv4_addr = V4_ADDR.parse::<Ipv4Addr>().unwrap();
+    CommandLineTest::new()
+        .flag("listen-address", Some(V6_ADDR))
+        .flag("listen-address", Some(V4_ADDR))
+        .run_with_zero_port()
+        .with_config(|config| {
+            assert_eq!(
+                config.network.listen_addrs().v6().map(|addr| addr.addr),
+                Some(ipv6_addr)
+            );
+            assert_eq!(
+                config.network.listen_addrs().v4().map(|addr| addr.addr),
+                Some(ipv4_addr)
+            )
+        });
+}
+#[test]
+#[should_panic]
+fn network_listen_address_flag_wrong_double_v4_value_config() {
+    // It's actually possible to listen over multiple sockets in libp2p over the same ip version.
+    // However this is not compatible with the single contactable address over each version in ENR.
+    // Because of this, it's important to test this is disallowed.
+    const V4_ADDR1: &str = "127.0.0.1";
+    const V4_ADDR2: &str = "0.0.0.0";
+    CommandLineTest::new()
+        .flag("listen-address", Some(V4_ADDR1))
+        .flag("listen-address", Some(V4_ADDR2))
+        .run_with_zero_port();
+}
+#[test]
+#[should_panic]
+fn network_listen_address_flag_wrong_double_v6_value_config() {
+    // It's actually possible to listen over multiple sockets in libp2p over the same ip version.
+    // However this is not compatible with the single contactable address over each version in ENR.
+    // Because of this, it's important to test this is disallowed.
+    const V6_ADDR1: &str = "::3";
+    const V6_ADDR2: &str = "::1";
+    CommandLineTest::new()
+        .flag("listen-address", Some(V6_ADDR1))
+        .flag("listen-address", Some(V6_ADDR2))
+        .run_with_zero_port();
+}
+#[test]
+fn network_port_flag_over_ipv4() {
+    let port = unused_tcp4_port().expect("Unable to find unused port.");
     CommandLineTest::new()
         .flag("port", Some(port.to_string().as_str()))
         .run()
         .with_config(|config| {
-            assert_eq!(config.network.libp2p_port, port);
-            assert_eq!(config.network.discovery_port, port);
+            assert_eq!(
+                config
+                    .network
+                    .listen_addrs()
+                    .v4()
+                    .map(|listen_addr| (listen_addr.udp_port, listen_addr.tcp_port)),
+                Some((port, port))
+            );
         });
 }
 #[test]
-fn network_port_and_discovery_port_flags() {
-    let port1 = unused_tcp_port().expect("Unable to find unused port.");
-    let port2 = unused_udp_port().expect("Unable to find unused port.");
+fn network_port_flag_over_ipv6() {
+    let port = unused_tcp6_port().expect("Unable to find unused port.");
     CommandLineTest::new()
-        .flag("port", Some(port1.to_string().as_str()))
-        .flag("discovery-port", Some(port2.to_string().as_str()))
+        .flag("listen-address", Some("::1"))
+        .flag("port", Some(port.to_string().as_str()))
         .run()
         .with_config(|config| {
-            assert_eq!(config.network.libp2p_port, port1);
-            assert_eq!(config.network.discovery_port, port2);
+            assert_eq!(
+                config
+                    .network
+                    .listen_addrs()
+                    .v6()
+                    .map(|listen_addr| (listen_addr.udp_port, listen_addr.tcp_port)),
+                Some((port, port))
+            );
         });
 }
+#[test]
+fn network_port_and_discovery_port_flags_over_ipv4() {
+    let tcp4_port = unused_tcp4_port().expect("Unable to find unused port.");
+    let udp4_port = unused_udp4_port().expect("Unable to find unused port.");
+    CommandLineTest::new()
+        .flag("port", Some(tcp4_port.to_string().as_str()))
+        .flag("discovery-port", Some(udp4_port.to_string().as_str()))
+        .run()
+        .with_config(|config| {
+            assert_eq!(
+                config
+                    .network
+                    .listen_addrs()
+                    .v4()
+                    .map(|listen_addr| (listen_addr.tcp_port, listen_addr.udp_port)),
+                Some((tcp4_port, udp4_port))
+            );
+        });
+}
+#[test]
+fn network_port_and_discovery_port_flags_over_ipv6() {
+    let tcp6_port = unused_tcp6_port().expect("Unable to find unused port.");
+    let udp6_port = unused_udp6_port().expect("Unable to find unused port.");
+    CommandLineTest::new()
+        .flag("listen-address", Some("::1"))
+        .flag("port", Some(tcp6_port.to_string().as_str()))
+        .flag("discovery-port", Some(udp6_port.to_string().as_str()))
+        .run()
+        .with_config(|config| {
+            assert_eq!(
+                config
+                    .network
+                    .listen_addrs()
+                    .v6()
+                    .map(|listen_addr| (listen_addr.tcp_port, listen_addr.udp_port)),
+                Some((tcp6_port, udp6_port))
+            );
+        });
+}
+#[test]
+fn network_port_and_discovery_port_flags_over_ipv4_and_ipv6() {
+    let tcp4_port = unused_tcp4_port().expect("Unable to find unused port.");
+    let udp4_port = unused_udp4_port().expect("Unable to find unused port.");
+    let tcp6_port = unused_tcp6_port().expect("Unable to find unused port.");
+    let udp6_port = unused_udp6_port().expect("Unable to find unused port.");
+    CommandLineTest::new()
+        .flag("listen-address", Some("::1"))
+        .flag("listen-address", Some("127.0.0.1"))
+        .flag("port", Some(tcp4_port.to_string().as_str()))
+        .flag("discovery-port", Some(udp4_port.to_string().as_str()))
+        .flag("port6", Some(tcp6_port.to_string().as_str()))
+        .flag("discovery-port6", Some(udp6_port.to_string().as_str()))
+        .run()
+        .with_config(|config| {
+            assert_eq!(
+                config
+                    .network
+                    .listen_addrs()
+                    .v4()
+                    .map(|listen_addr| (listen_addr.tcp_port, listen_addr.udp_port)),
+                Some((tcp4_port, udp4_port))
+            );
+
+            assert_eq!(
+                config
+                    .network
+                    .listen_addrs()
+                    .v6()
+                    .map(|listen_addr| (listen_addr.tcp_port, listen_addr.udp_port)),
+                Some((tcp6_port, udp6_port))
+            );
+        });
+}
+
 #[test]
 fn disable_discovery_flag() {
     CommandLineTest::new()
@@ -986,7 +1137,6 @@ fn zero_ports_flag() {
     CommandLineTest::new()
         .run_with_zero_port()
         .with_config(|config| {
-            assert_eq!(config.network.enr_address, None);
             assert_eq!(config.http_api.listen_port, 0);
             assert_eq!(config.http_metrics.listen_port, 0);
         });
@@ -1003,67 +1153,171 @@ fn network_load_flag() {
 
 // Tests for ENR flags.
 #[test]
-fn enr_udp_port_flags() {
-    let port = unused_udp_port().expect("Unable to find unused port.");
+fn enr_udp_port_flag() {
+    let port = unused_udp4_port().expect("Unable to find unused port.");
     CommandLineTest::new()
         .flag("enr-udp-port", Some(port.to_string().as_str()))
         .run_with_zero_port()
-        .with_config(|config| assert_eq!(config.network.enr_udp_port, Some(port)));
+        .with_config(|config| assert_eq!(config.network.enr_udp4_port, Some(port)));
 }
 #[test]
-fn enr_tcp_port_flags() {
-    let port = unused_tcp_port().expect("Unable to find unused port.");
+fn enr_tcp_port_flag() {
+    let port = unused_tcp4_port().expect("Unable to find unused port.");
     CommandLineTest::new()
         .flag("enr-tcp-port", Some(port.to_string().as_str()))
         .run_with_zero_port()
-        .with_config(|config| assert_eq!(config.network.enr_tcp_port, Some(port)));
+        .with_config(|config| assert_eq!(config.network.enr_tcp4_port, Some(port)));
 }
 #[test]
-fn enr_match_flag() {
-    let addr = "127.0.0.2".parse::<IpAddr>().unwrap();
-    let port1 = unused_udp_port().expect("Unable to find unused port.");
-    let port2 = unused_udp_port().expect("Unable to find unused port.");
+fn enr_udp6_port_flag() {
+    let port = unused_udp6_port().expect("Unable to find unused port.");
+    CommandLineTest::new()
+        .flag("enr-udp6-port", Some(port.to_string().as_str()))
+        .run_with_zero_port()
+        .with_config(|config| assert_eq!(config.network.enr_udp6_port, Some(port)));
+}
+#[test]
+fn enr_tcp6_port_flag() {
+    let port = unused_tcp6_port().expect("Unable to find unused port.");
+    CommandLineTest::new()
+        .flag("enr-tcp6-port", Some(port.to_string().as_str()))
+        .run_with_zero_port()
+        .with_config(|config| assert_eq!(config.network.enr_tcp6_port, Some(port)));
+}
+#[test]
+fn enr_match_flag_over_ipv4() {
+    let addr = "127.0.0.2".parse::<Ipv4Addr>().unwrap();
+    let udp4_port = unused_udp4_port().expect("Unable to find unused port.");
+    let tcp4_port = unused_tcp4_port().expect("Unable to find unused port.");
     CommandLineTest::new()
         .flag("enr-match", None)
         .flag("listen-address", Some("127.0.0.2"))
-        .flag("discovery-port", Some(port1.to_string().as_str()))
-        .flag("port", Some(port2.to_string().as_str()))
+        .flag("discovery-port", Some(udp4_port.to_string().as_str()))
+        .flag("port", Some(tcp4_port.to_string().as_str()))
         .run()
         .with_config(|config| {
-            assert_eq!(config.network.listen_address, addr);
-            assert_eq!(config.network.enr_address, Some(addr));
-            assert_eq!(config.network.discovery_port, port1);
-            assert_eq!(config.network.enr_udp_port, Some(port1));
+            assert_eq!(
+                config.network.listen_addrs().v4().map(|listen_addr| (
+                    listen_addr.addr,
+                    listen_addr.udp_port,
+                    listen_addr.tcp_port
+                )),
+                Some((addr, udp4_port, tcp4_port))
+            );
+            assert_eq!(config.network.enr_address, (Some(addr), None));
+            assert_eq!(config.network.enr_udp4_port, Some(udp4_port));
         });
 }
 #[test]
-fn enr_address_flag() {
-    let addr = "192.167.1.1".parse::<IpAddr>().unwrap();
-    let port = unused_udp_port().expect("Unable to find unused port.");
+fn enr_match_flag_over_ipv6() {
+    const ADDR: &str = "::1";
+    let addr = ADDR.parse::<Ipv6Addr>().unwrap();
+    let udp6_port = unused_udp6_port().expect("Unable to find unused port.");
+    let tcp6_port = unused_tcp6_port().expect("Unable to find unused port.");
+    CommandLineTest::new()
+        .flag("enr-match", None)
+        .flag("listen-address", Some(ADDR))
+        .flag("discovery-port", Some(udp6_port.to_string().as_str()))
+        .flag("port", Some(tcp6_port.to_string().as_str()))
+        .run()
+        .with_config(|config| {
+            assert_eq!(
+                config.network.listen_addrs().v6().map(|listen_addr| (
+                    listen_addr.addr,
+                    listen_addr.udp_port,
+                    listen_addr.tcp_port
+                )),
+                Some((addr, udp6_port, tcp6_port))
+            );
+            assert_eq!(config.network.enr_address, (None, Some(addr)));
+            assert_eq!(config.network.enr_udp6_port, Some(udp6_port));
+        });
+}
+#[test]
+fn enr_match_flag_over_ipv4_and_ipv6() {
+    const IPV6_ADDR: &str = "::1";
+    let ipv6_addr = IPV6_ADDR.parse::<Ipv6Addr>().unwrap();
+    let udp6_port = unused_udp6_port().expect("Unable to find unused port.");
+    let tcp6_port = unused_tcp6_port().expect("Unable to find unused port.");
+    const IPV4_ADDR: &str = "127.0.0.1";
+    let ipv4_addr = IPV4_ADDR.parse::<Ipv4Addr>().unwrap();
+    let udp4_port = unused_udp4_port().expect("Unable to find unused port.");
+    let tcp4_port = unused_tcp4_port().expect("Unable to find unused port.");
+    CommandLineTest::new()
+        .flag("enr-match", None)
+        .flag("listen-address", Some(IPV4_ADDR))
+        .flag("discovery-port", Some(udp4_port.to_string().as_str()))
+        .flag("port", Some(tcp4_port.to_string().as_str()))
+        .flag("listen-address", Some(IPV6_ADDR))
+        .flag("discovery-port6", Some(udp6_port.to_string().as_str()))
+        .flag("port6", Some(tcp6_port.to_string().as_str()))
+        .run()
+        .with_config(|config| {
+            assert_eq!(
+                config.network.listen_addrs().v6().map(|listen_addr| (
+                    listen_addr.addr,
+                    listen_addr.udp_port,
+                    listen_addr.tcp_port
+                )),
+                Some((ipv6_addr, udp6_port, tcp6_port))
+            );
+            assert_eq!(
+                config.network.listen_addrs().v4().map(|listen_addr| (
+                    listen_addr.addr,
+                    listen_addr.udp_port,
+                    listen_addr.tcp_port
+                )),
+                Some((ipv4_addr, udp4_port, tcp4_port))
+            );
+            assert_eq!(
+                config.network.enr_address,
+                (Some(ipv4_addr), Some(ipv6_addr))
+            );
+            assert_eq!(config.network.enr_udp6_port, Some(udp6_port));
+            assert_eq!(config.network.enr_udp4_port, Some(udp4_port));
+        });
+}
+#[test]
+fn enr_address_flag_with_ipv4() {
+    let addr = "192.167.1.1".parse::<Ipv4Addr>().unwrap();
+    let port = unused_udp4_port().expect("Unable to find unused port.");
     CommandLineTest::new()
         .flag("enr-address", Some("192.167.1.1"))
         .flag("enr-udp-port", Some(port.to_string().as_str()))
         .run_with_zero_port()
         .with_config(|config| {
-            assert_eq!(config.network.enr_address, Some(addr));
-            assert_eq!(config.network.enr_udp_port, Some(port));
+            assert_eq!(config.network.enr_address, (Some(addr), None));
+            assert_eq!(config.network.enr_udp4_port, Some(port));
+        });
+}
+#[test]
+fn enr_address_flag_with_ipv6() {
+    let addr = "192.167.1.1".parse::<Ipv4Addr>().unwrap();
+    let port = unused_udp4_port().expect("Unable to find unused port.");
+    CommandLineTest::new()
+        .flag("enr-address", Some("192.167.1.1"))
+        .flag("enr-udp-port", Some(port.to_string().as_str()))
+        .run_with_zero_port()
+        .with_config(|config| {
+            assert_eq!(config.network.enr_address, (Some(addr), None));
+            assert_eq!(config.network.enr_udp4_port, Some(port));
         });
 }
 #[test]
 fn enr_address_dns_flag() {
-    let addr = "127.0.0.1".parse::<IpAddr>().unwrap();
-    let ipv6addr = "::1".parse::<IpAddr>().unwrap();
-    let port = unused_udp_port().expect("Unable to find unused port.");
+    let addr = Ipv4Addr::LOCALHOST;
+    let ipv6addr = Ipv6Addr::LOCALHOST;
+    let port = unused_udp4_port().expect("Unable to find unused port.");
     CommandLineTest::new()
         .flag("enr-address", Some("localhost"))
         .flag("enr-udp-port", Some(port.to_string().as_str()))
         .run_with_zero_port()
         .with_config(|config| {
             assert!(
-                config.network.enr_address == Some(addr)
-                    || config.network.enr_address == Some(ipv6addr)
+                config.network.enr_address.0 == Some(addr)
+                    || config.network.enr_address.1 == Some(ipv6addr)
             );
-            assert_eq!(config.network.enr_udp_port, Some(port));
+            assert_eq!(config.network.enr_udp4_port, Some(port));
         });
 }
 #[test]
@@ -1100,8 +1354,8 @@ fn http_address_ipv6_flag() {
 }
 #[test]
 fn http_port_flag() {
-    let port1 = unused_tcp_port().expect("Unable to find unused port.");
-    let port2 = unused_tcp_port().expect("Unable to find unused port.");
+    let port1 = unused_tcp4_port().expect("Unable to find unused port.");
+    let port2 = unused_tcp4_port().expect("Unable to find unused port.");
     CommandLineTest::new()
         .flag("http-port", Some(port1.to_string().as_str()))
         .flag("port", Some(port2.to_string().as_str()))
@@ -1215,8 +1469,8 @@ fn metrics_address_ipv6_flag() {
 }
 #[test]
 fn metrics_port_flag() {
-    let port1 = unused_tcp_port().expect("Unable to find unused port.");
-    let port2 = unused_tcp_port().expect("Unable to find unused port.");
+    let port1 = unused_tcp4_port().expect("Unable to find unused port.");
+    let port2 = unused_tcp4_port().expect("Unable to find unused port.");
     CommandLineTest::new()
         .flag("metrics", None)
         .flag("metrics-port", Some(port1.to_string().as_str()))
diff --git a/lighthouse/tests/boot_node.rs b/lighthouse/tests/boot_node.rs
index 8c000bbb3..4dd5ad95d 100644
--- a/lighthouse/tests/boot_node.rs
+++ b/lighthouse/tests/boot_node.rs
@@ -12,7 +12,7 @@ use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::str::FromStr;
 use tempfile::TempDir;
-use unused_port::unused_udp_port;
+use unused_port::unused_udp4_port;
 
 const IP_ADDRESS: &str = "192.168.2.108";
 
@@ -62,7 +62,7 @@ fn enr_address_arg() {
 
 #[test]
 fn port_flag() {
-    let port = unused_udp_port().unwrap();
+    let port = unused_udp4_port().unwrap();
     CommandLineTest::new()
         .flag("port", Some(port.to_string().as_str()))
         .run_with_ip()
@@ -122,7 +122,7 @@ fn boot_nodes_flag() {
 
 #[test]
 fn enr_port_flag() {
-    let port = unused_udp_port().unwrap();
+    let port = unused_udp4_port().unwrap();
     CommandLineTest::new()
         .flag("enr-port", Some(port.to_string().as_str()))
         .run_with_ip()
diff --git a/testing/eth1_test_rig/src/ganache.rs b/testing/eth1_test_rig/src/ganache.rs
index d8df3fd8a..898a089ba 100644
--- a/testing/eth1_test_rig/src/ganache.rs
+++ b/testing/eth1_test_rig/src/ganache.rs
@@ -3,7 +3,7 @@ use std::io::prelude::*;
 use std::io::BufReader;
 use std::process::{Child, Command, Stdio};
 use std::time::{Duration, Instant};
-use unused_port::unused_tcp_port;
+use unused_port::unused_tcp4_port;
 use web3::{transports::Http, Transport, Web3};
 
 /// How long we will wait for ganache to indicate that it is ready.
@@ -65,7 +65,7 @@ impl GanacheInstance {
     /// Start a new `ganache` process, waiting until it indicates that it is ready to accept
     /// RPC connections.
     pub fn new(chain_id: u64) -> Result<Self, String> {
-        let port = unused_tcp_port()?;
+        let port = unused_tcp4_port()?;
         let binary = match cfg!(windows) {
             true => "ganache.cmd",
             false => "ganache",
@@ -97,7 +97,7 @@ impl GanacheInstance {
     }
 
     pub fn fork(&self) -> Result<Self, String> {
-        let port = unused_tcp_port()?;
+        let port = unused_tcp4_port()?;
         let binary = match cfg!(windows) {
             true => "ganache.cmd",
             false => "ganache",
diff --git a/testing/execution_engine_integration/src/execution_engine.rs b/testing/execution_engine_integration/src/execution_engine.rs
index ad5af5315..61a50b040 100644
--- a/testing/execution_engine_integration/src/execution_engine.rs
+++ b/testing/execution_engine_integration/src/execution_engine.rs
@@ -4,7 +4,7 @@ use sensitive_url::SensitiveUrl;
 use std::path::PathBuf;
 use std::process::Child;
 use tempfile::TempDir;
-use unused_port::unused_tcp_port;
+use unused_port::unused_tcp4_port;
 
 pub const KEYSTORE_PASSWORD: &str = "testpwd";
 pub const ACCOUNT1: &str = "7b8C3a386C0eea54693fFB0DA17373ffC9228139";
@@ -50,8 +50,8 @@ impl<E: GenericExecutionEngine> ExecutionEngine<E> {
     pub fn new(engine: E) -> Self {
         let datadir = E::init_datadir();
         let jwt_secret_path = datadir.path().join(DEFAULT_JWT_FILE);
-        let http_port = unused_tcp_port().unwrap();
-        let http_auth_port = unused_tcp_port().unwrap();
+        let http_port = unused_tcp4_port().unwrap();
+        let http_auth_port = unused_tcp4_port().unwrap();
         let child = E::start_client(&datadir, http_port, http_auth_port, jwt_secret_path);
         let provider = Provider::<Http>::try_from(format!("http://localhost:{}", http_port))
             .expect("failed to instantiate ethers provider");
diff --git a/testing/execution_engine_integration/src/geth.rs b/testing/execution_engine_integration/src/geth.rs
index 1b96fa9f3..5c83a97e2 100644
--- a/testing/execution_engine_integration/src/geth.rs
+++ b/testing/execution_engine_integration/src/geth.rs
@@ -5,7 +5,7 @@ use std::path::{Path, PathBuf};
 use std::process::{Child, Command, Output};
 use std::{env, fs::File};
 use tempfile::TempDir;
-use unused_port::unused_tcp_port;
+use unused_port::unused_tcp4_port;
 
 const GETH_BRANCH: &str = "master";
 const GETH_REPO_URL: &str = "https://github.com/ethereum/go-ethereum";
@@ -83,7 +83,7 @@ impl GenericExecutionEngine for GethEngine {
         http_auth_port: u16,
         jwt_secret_path: PathBuf,
     ) -> Child {
-        let network_port = unused_tcp_port().unwrap();
+        let network_port = unused_tcp4_port().unwrap();
 
         Command::new(Self::binary_path())
             .arg("--datadir")
diff --git a/testing/execution_engine_integration/src/main.rs b/testing/execution_engine_integration/src/main.rs
index bd3436602..e46bc13c8 100644
--- a/testing/execution_engine_integration/src/main.rs
+++ b/testing/execution_engine_integration/src/main.rs
@@ -1,4 +1,3 @@
-#![recursion_limit = "1024"]
 /// This binary runs integration tests between Lighthouse and execution engines.
 ///
 /// It will first attempt to build any supported integration clients, then it will run tests.
diff --git a/testing/execution_engine_integration/src/nethermind.rs b/testing/execution_engine_integration/src/nethermind.rs
index 740d87ab8..720a4a73b 100644
--- a/testing/execution_engine_integration/src/nethermind.rs
+++ b/testing/execution_engine_integration/src/nethermind.rs
@@ -6,7 +6,7 @@ use std::fs::File;
 use std::path::{Path, PathBuf};
 use std::process::{Child, Command, Output};
 use tempfile::TempDir;
-use unused_port::unused_tcp_port;
+use unused_port::unused_tcp4_port;
 
 /// We've pinned the Nethermind version since our method of using the `master` branch to
 /// find the latest tag isn't working. It appears Nethermind don't always tag on `master`.
@@ -88,7 +88,7 @@ impl GenericExecutionEngine for NethermindEngine {
         http_auth_port: u16,
         jwt_secret_path: PathBuf,
     ) -> Child {
-        let network_port = unused_tcp_port().unwrap();
+        let network_port = unused_tcp4_port().unwrap();
         let genesis_json_path = datadir.path().join("genesis.json");
 
         Command::new(Self::binary_path())
diff --git a/testing/node_test_rig/src/lib.rs b/testing/node_test_rig/src/lib.rs
index 82a60cda2..d4fd115be 100644
--- a/testing/node_test_rig/src/lib.rs
+++ b/testing/node_test_rig/src/lib.rs
@@ -89,8 +89,9 @@ pub fn testing_client_config() -> ClientConfig {
     let mut client_config = ClientConfig::default();
 
     // Setting ports to `0` means that the OS will choose some available port.
-    client_config.network.libp2p_port = 0;
-    client_config.network.discovery_port = 0;
+    client_config
+        .network
+        .set_ipv4_listening_address(std::net::Ipv4Addr::UNSPECIFIED, 0, 0);
     client_config.network.upnp_enabled = false;
     client_config.http_api.enabled = true;
     client_config.http_api.listen_port = 0;
diff --git a/testing/simulator/src/eth1_sim.rs b/testing/simulator/src/eth1_sim.rs
index 42aefea7a..43e8a5cf4 100644
--- a/testing/simulator/src/eth1_sim.rs
+++ b/testing/simulator/src/eth1_sim.rs
@@ -13,7 +13,7 @@ use node_test_rig::{
 use rayon::prelude::*;
 use sensitive_url::SensitiveUrl;
 use std::cmp::max;
-use std::net::{IpAddr, Ipv4Addr};
+use std::net::Ipv4Addr;
 use std::time::Duration;
 use tokio::time::sleep;
 use types::{Epoch, EthSpec, MinimalEthSpec};
@@ -149,7 +149,7 @@ pub fn run_eth1_sim(matches: &ArgMatches) -> Result<(), String> {
         beacon_config.eth1.chain_id = Eth1Id::from(chain_id);
         beacon_config.network.target_peers = node_count - 1;
 
-        beacon_config.network.enr_address = Some(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)));
+        beacon_config.network.enr_address = (Some(Ipv4Addr::LOCALHOST), None);
 
         if post_merge_sim {
             let el_config = execution_layer::Config {
diff --git a/testing/simulator/src/local_network.rs b/testing/simulator/src/local_network.rs
index 8df912ed1..3e481df88 100644
--- a/testing/simulator/src/local_network.rs
+++ b/testing/simulator/src/local_network.rs
@@ -58,10 +58,13 @@ impl<E: EthSpec> LocalNetwork<E> {
         context: RuntimeContext<E>,
         mut beacon_config: ClientConfig,
     ) -> Result<Self, String> {
-        beacon_config.network.discovery_port = BOOTNODE_PORT;
-        beacon_config.network.libp2p_port = BOOTNODE_PORT;
-        beacon_config.network.enr_udp_port = Some(BOOTNODE_PORT);
-        beacon_config.network.enr_tcp_port = Some(BOOTNODE_PORT);
+        beacon_config.network.set_ipv4_listening_address(
+            std::net::Ipv4Addr::UNSPECIFIED,
+            BOOTNODE_PORT,
+            BOOTNODE_PORT,
+        );
+        beacon_config.network.enr_udp4_port = Some(BOOTNODE_PORT);
+        beacon_config.network.enr_tcp4_port = Some(BOOTNODE_PORT);
         beacon_config.network.discv5_config.table_filter = |_| true;
 
         let execution_node = if let Some(el_config) = &mut beacon_config.execution_layer {
@@ -132,10 +135,13 @@ impl<E: EthSpec> LocalNetwork<E> {
                     .enr()
                     .expect("bootnode must have a network"),
             );
-            beacon_config.network.discovery_port = BOOTNODE_PORT + count;
-            beacon_config.network.libp2p_port = BOOTNODE_PORT + count;
-            beacon_config.network.enr_udp_port = Some(BOOTNODE_PORT + count);
-            beacon_config.network.enr_tcp_port = Some(BOOTNODE_PORT + count);
+            beacon_config.network.set_ipv4_listening_address(
+                std::net::Ipv4Addr::UNSPECIFIED,
+                BOOTNODE_PORT + count,
+                BOOTNODE_PORT + count,
+            );
+            beacon_config.network.enr_udp4_port = Some(BOOTNODE_PORT + count);
+            beacon_config.network.enr_tcp4_port = Some(BOOTNODE_PORT + count);
             beacon_config.network.discv5_config.table_filter = |_| true;
         }
         if let Some(el_config) = &mut beacon_config.execution_layer {
diff --git a/testing/simulator/src/main.rs b/testing/simulator/src/main.rs
index 0627ba7dd..922149537 100644
--- a/testing/simulator/src/main.rs
+++ b/testing/simulator/src/main.rs
@@ -1,5 +1,3 @@
-#![recursion_limit = "512"]
-
 //! This crate provides a simluation that creates `n` beacon node and validator clients, each with
 //! `v` validators. A deposit contract is deployed at the start of the simulation using a local
 //! `ganache` instance (you must have `ganache` installed and avaliable on your path). All
diff --git a/testing/simulator/src/no_eth1_sim.rs b/testing/simulator/src/no_eth1_sim.rs
index 1a026ded4..f1f6dc442 100644
--- a/testing/simulator/src/no_eth1_sim.rs
+++ b/testing/simulator/src/no_eth1_sim.rs
@@ -7,7 +7,7 @@ use node_test_rig::{
 };
 use rayon::prelude::*;
 use std::cmp::max;
-use std::net::{IpAddr, Ipv4Addr};
+use std::net::Ipv4Addr;
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 use tokio::time::sleep;
 use types::{Epoch, EthSpec, MainnetEthSpec};
@@ -91,7 +91,7 @@ pub fn run_no_eth1_sim(matches: &ArgMatches) -> Result<(), String> {
     beacon_config.dummy_eth1_backend = true;
     beacon_config.sync_eth1_chain = true;
 
-    beacon_config.network.enr_address = Some(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)));
+    beacon_config.network.enr_address = (Some(Ipv4Addr::LOCALHOST), None);
 
     let main_future = async {
         let network = LocalNetwork::new(context.clone(), beacon_config.clone()).await?;
diff --git a/testing/simulator/src/sync_sim.rs b/testing/simulator/src/sync_sim.rs
index 9d759715e..c437457c2 100644
--- a/testing/simulator/src/sync_sim.rs
+++ b/testing/simulator/src/sync_sim.rs
@@ -8,7 +8,7 @@ use node_test_rig::{
 };
 use node_test_rig::{testing_validator_config, ClientConfig};
 use std::cmp::max;
-use std::net::{IpAddr, Ipv4Addr};
+use std::net::Ipv4Addr;
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 use types::{Epoch, EthSpec};
 
@@ -95,7 +95,7 @@ fn syncing_sim(
 
     beacon_config.http_api.allow_sync_stalled = true;
 
-    beacon_config.network.enr_address = Some(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)));
+    beacon_config.network.enr_address = (Some(Ipv4Addr::LOCALHOST), None);
 
     // Generate the directories and keystores required for the validator clients.
     let validator_indices = (0..num_validators).collect::<Vec<_>>();