Add comment and minor fix.

compose/docker-compose-fixturenet-eth.yml

@@ -77,6 +77,8 @@ services:
       fixturenet-eth-net:
 
 networks:
+  # When the bootnode ENR is generated during the build, it requires a specific IP.
+  # The easiest way to do that is to use a private network.
   fixturenet-eth-net:
     driver: bridge
     ipam:

container-build/cerc-fixturenet-eth-lighthouse/genesis/cl/beacon_node.sh

@@ -19,7 +19,6 @@ http_port=8001
 authrpc_port=8551
 
 ENR=`cat $DATADIR/bootnode/enr.dat`
-ENR_IP=`ip addr | grep 172 | awk '{print $2}' | cut -d '/' -f1`
 
 exec lighthouse \
   --debug-level $DEBUG_LEVEL \
@@ -30,7 +29,7 @@ exec lighthouse \
   --testnet-dir $TESTNET_DIR \
   --enable-private-discovery \
   --staking \
-  --enr-address $ENR_IP \
+  --enr-address $BOOTNODE_IP \
   --enr-udp-port $network_port \
   --enr-tcp-port $network_port \
   --port $network_port \