diff --git a/metropolis/node/net_protocols.go b/metropolis/node/net_protocols.go
new file mode 100644
index 0000000..ac43cbf
--- /dev/null
+++ b/metropolis/node/net_protocols.go
@@ -0,0 +1,11 @@
+package node
+
+import "github.com/vishvananda/netlink"
+
+// These are netlink protocol numbers used internally for various netlink
+// resource (e.g. route) owners/manager.
+const (
+	// ProtocolClusternet is used by //metropolis/node/core/clusternet when
+	// creating/removing routes pointing to the clusternet interface.
+	ProtocolClusternet netlink.RouteProtocol = 129
+)