diff --git a/README.rst b/README.rst
index 25eb136..098305b 100644
--- a/README.rst
+++ b/README.rst
@@ -741,7 +741,7 @@
           engine: ml2
           tenant_network_types: "flat,vlan" # Can be mixed flat,vlan,vxlan
           tenant_vlan_range: "1000:2000"
-          external_vlan_range: "100:200" # Does not have to be defined.
+          external_vlan_range: "100:200" # Does not have to be defined. Use "0:4096" for accepting all vlans.
           external_mtu: 9000
           mechanism:
             ovs: