diff --git a/p2p/protocol/identify/obsaddr.go b/p2p/protocol/identify/obsaddr.go
index 5d339a806d..1fd8eb7184 100644
--- a/p2p/protocol/identify/obsaddr.go
+++ b/p2p/protocol/identify/obsaddr.go
@@ -70,15 +70,24 @@ func (oa *ObservedAddr) numInbound() int {
 	return count
 }
 
+// GroupKey returns the group in which this observation belongs. Currently, an
+// observed address's group is just the address with all ports set to 0. This
+// means we can advertise the most commonly observed external ports without
+// advertising _every_ observed port.
 func (oa *ObservedAddr) GroupKey() string {
-	key := ""
-	protos := oa.Addr.Protocols()
-
-	for i := range protos {
-		key = key + "/" + protos[i].Name
-	}
+	key := make([]byte, 0, len(oa.Addr.Bytes()))
+	ma.ForEach(oa.Addr, func(c ma.Component) bool {
+		switch proto := c.Protocol(); proto.Code {
+		case ma.P_TCP, ma.P_UDP:
+			key = append(key, proto.VCode...)
+			key = append(key, 0, 0) // zero in two bytes
+		default:
+			key = append(key, c.Bytes()...)
+		}
+		return true
+	})
 
-	return key
+	return string(key)
 }
 
 type newObservation struct {
diff --git a/p2p/protocol/identify/obsaddr_test.go b/p2p/protocol/identify/obsaddr_test.go
index 2beab1a674..a0f50cf975 100644
--- a/p2p/protocol/identify/obsaddr_test.go
+++ b/p2p/protocol/identify/obsaddr_test.go
@@ -314,17 +314,28 @@ func TestObservedAddrFiltering(t *testing.T) {
 }
 
 func TestObservedAddrGroupKey(t *testing.T) {
-	oa1 := &identify.ObservedAddr{Addr: ma.StringCast("/ip4/1.2.3.4/tcp/1231")}
-	require.Equal(t, "/ip4/tcp", oa1.GroupKey())
-
-	oa2 := &identify.ObservedAddr{Addr: ma.StringCast("/ip4/1.2.3.5/tcp/2222")}
-	require.Equal(t, "/ip4/tcp", oa2.GroupKey())
-
-	oa3 := &identify.ObservedAddr{Addr: ma.StringCast("/ip4/1.2.3.4/udp/1231")}
-	require.Equal(t, "/ip4/udp", oa3.GroupKey())
-	oa4 := &identify.ObservedAddr{Addr: ma.StringCast("/ip4/1.3.3.4/udp/1531")}
-	require.Equal(t, "/ip4/udp", oa4.GroupKey())
-
-	oa5 := &identify.ObservedAddr{Addr: ma.StringCast("/ip4/1.3.3.4/udp/1531/quic")}
-	require.Equal(t, "/ip4/udp/quic", oa5.GroupKey())
+	oa1 := &identify.ObservedAddr{Addr: ma.StringCast("/ip4/1.2.3.4/tcp/2345")}
+	oa2 := &identify.ObservedAddr{Addr: ma.StringCast("/ip4/1.2.3.4/tcp/1231")}
+	oa3 := &identify.ObservedAddr{Addr: ma.StringCast("/ip4/1.2.3.5/tcp/1231")}
+	oa4 := &identify.ObservedAddr{Addr: ma.StringCast("/ip4/1.2.3.4/udp/1231")}
+	oa5 := &identify.ObservedAddr{Addr: ma.StringCast("/ip4/1.2.3.4/udp/1531")}
+	oa6 := &identify.ObservedAddr{Addr: ma.StringCast("/ip4/1.2.3.4/udp/1531/quic")}
+	oa7 := &identify.ObservedAddr{Addr: ma.StringCast("/ip4/1.2.3.4/udp/1111/quic")}
+	oa8 := &identify.ObservedAddr{Addr: ma.StringCast("/ip4/1.2.3.5/udp/1111/quic")}
+
+	// different ports, same IP => same key
+	require.Equal(t, oa1.GroupKey(), oa2.GroupKey())
+	// different IPs => different key
+	require.NotEqual(t, oa2.GroupKey(), oa3.GroupKey())
+	// same port, different protos => different keys
+	require.NotEqual(t, oa3.GroupKey(), oa4.GroupKey())
+	// same port, same address, different protos => different keys
+	require.NotEqual(t, oa2.GroupKey(), oa4.GroupKey())
+	// udp works as well
+	require.Equal(t, oa4.GroupKey(), oa5.GroupKey())
+	// udp and quic are different
+	require.NotEqual(t, oa5.GroupKey(), oa6.GroupKey())
+	// quic works as well
+	require.Equal(t, oa6.GroupKey(), oa7.GroupKey())
+	require.NotEqual(t, oa7.GroupKey(), oa8.GroupKey())
 }