diff --git a/metropolis/node/net_protocols.go b/metropolis/node/net_protocols.go
index 2e005fb..26dd0c0 100644
--- a/metropolis/node/net_protocols.go
+++ b/metropolis/node/net_protocols.go
@@ -7,3 +7,13 @@
 	// creating/removing routes pointing to the clusternet interface.
 	ProtocolClusternet int = 129
 )
+
+// Netlink link groups used for interface classification and traffic matching.
+const (
+	// LinkGroupK8sPod is set on all host side PtP interfaces going to K8s
+	// pods.
+	LinkGroupK8sPod uint32 = 8
+	// LinkGroupClusternet is set on all interfaces not needing SNAT from the
+	// K8s internal IPs.
+	LinkGroupClusternet uint32 = 9
+)