Is it ready for review? If not, could you convert it to draft?

@nalepae Just waiting on a green CI. Will add you as a reviewer once green.

@nalepae Will add Hoodi test instructions and then move out of Draft status.

@nalepae

bazel run //cmd/beacon-chain:beacon-chain --config=release -- \
  --hoodi \
  --execution-endpoint=http://localhost:8551 \
  --jwt-secret={jwt_file}
  --checkpoint-sync-url=https://hoodi.beaconstate.ethstaker.cc/ \
  --genesis-beacon-api-url=https://hoodi.beaconstate.ethstaker.cc/ \
  --verbosity=info \
  --accept-terms-of-use \
  --datadir=beacon-hoodi-data \
  --log-file=beacon-hoodi.log \
  --enable-autonat

[2025-12-08 13:27:11.37] INFO p2p: AutoNAT v2 enabled for address reachability detection

The log line to print out reachability will only be emitted if your node has public addresses configured AND all peers in the network upgrade to the AutoNATV2 protocol. (which will happen after they run this change).

I've also added a unit test that verifies that the logs are outputted correctly once the corresponding libp2p event fires.

Hey @aarshkshah1992, you beat me to it! That was fast.
How about adding some metrics?

diff --git a/beacon-chain/p2p/monitoring.go b/beacon-chain/p2p/monitoring.go
index b454d2587d..37fa5ac9d6 100644
--- a/beacon-chain/p2p/monitoring.go
+++ b/beacon-chain/p2p/monitoring.go
@@ -185,6 +185,16 @@ var (
                Help: "The number of publish messages sent via rpc for a particular topic",
        },
                []string{"topic"})
+
+       // AutoNAT metrics
+       autonatReachableAddrs = promauto.NewGauge(prometheus.GaugeOpts{
+               Name: "p2p_autonat_reachable_addresses",
+               Help: "Number of addresses confirmed reachable via AutoNAT.",
+       })
+       autonatUnreachableAddrs = promauto.NewGauge(prometheus.GaugeOpts{
+               Name: "p2p_autonat_unreachable_addresses",
+               Help: "Number of addresses confirmed unreachable via AutoNAT.",
+       })
 )

 func (s *Service) updateMetrics() {
diff --git a/beacon-chain/p2p/service.go b/beacon-chain/p2p/service.go
index b9a4242c15..27270e08da 100644
--- a/beacon-chain/p2p/service.go
+++ b/beacon-chain/p2p/service.go
@@ -587,6 +587,10 @@ func (s *Service) subscribeReachabilityEvents() {
                                                "unreachable": multiaddrsToStrings(event.Unreachable),
                                                "unknown":     multiaddrsToStrings(event.Unknown),
                                        }).Info("Address reachability changed")
+
+                                       // Update Prometheus metrics
+                                       autonatReachableAddrs.Set(float64(len(event.Reachable)))
+                                       autonatUnreachableAddrs.Set(float64(len(event.Unreachable)))
                                }
                        }
                }

What does reachable, unknown and unreachable mean?
Why this is "unreachable" while the (redacted) IP address is exactly the good one to use?

[2025-12-09 10:54:46.95]  INFO p2p: Address reachability changed reachable=[] unknown=[/ip4/<redacted>/udp/13000/quic-v1] unreachable=[]

Then later:

[2025-12-09 10:55:16.95]  INFO p2p: Address reachability changed reachable=[] unknown=[/ip4/<redacted>/tcp/13000 /ip4/<redacted>/udp/13000/quic-v1] unreachable=[]

Now the node knows its public IP address, could it use it directly to advertise it on its own ENR instead of having to manually add the --p2p-host-ip=<public-ip> flag?

@willianpaixao I am not sure these metrics will be super helpful. Like you would want to know which addresses are reachable/unreachable but what exactly will you do with the count of those ? The logs should be good enough for your use case but let me know if you have any use for these metrics in mind.

What does reachable, unknown and unreachable mean? Why this is "unreachable" while the (redacted) IP address is exactly the good one to use?

[2025-12-09 10:54:46.95]  INFO p2p: Address reachability changed reachable=[] unknown=[/ip4/<redacted>/udp/13000/quic-v1] unreachable=[]

Then later:

[2025-12-09 10:55:16.95]  INFO p2p: Address reachability changed reachable=[] unknown=[/ip4/<redacted>/tcp/13000 /ip4/<redacted>/udp/13000/quic-v1] unreachable=[]

@nalepae

"reachable" means that enough peers running AutoNATV2 "servers" have dialed that address and confirmed that the dial went through. unreachable means that enough peers running AutoNATV2 "servers" have dialed that address and confirmed that the dial failed.

"unknown" means that we haven't recieved enough confirmations in either direction yet.

Now the node knows its public IP address, could it use it directly to advertise it on its own ENR instead of having to manually add the --p2p-host-ip=<public-ip> flag?

@nalepae This is done. We should still keep the "--p2p-host-ip=" flag but fallback to AutoNATV2 reachability if it is not configured.

@nalepae Are you happy to approve and merge this ? I've reverted the ENR update change.