Hidden Internal VLANs on a Cisco 6500

Something interesting about a Cisco 6500 is that it uses hidden internal VLANs. Most people will never be aware of this because the assignment starts in the extended VLAN range. An internal VLAN is created for every port in your chassis that is not an access port.

The command to view these VLANs is “show vlan internal usage“.

6509-router#show vlan internal usage

VLAN Usage
—- ——————–
1006 online diag vlan0
1007 online diag vlan1
1008 online diag vlan2
1009 online diag vlan3
1010 online diag vlan4
1011 online diag vlan5
1012 PM vlan process (trunk tagging)
1013 Control Plane Protection
1014 L3 multicast partial shortcuts for VPN 0
1015 Egress internal vlan
1016 Multicast VPN 0 QOS vlan
1017 IPv6 Multicast Egress multicast
1018 GigabitEthernet5/1
1019 vrf_0_vlan0
1020 GigabitEthernet6/2
1021 FastEthernet9/7
1022 FastEthernet9/6
1023 FastEthernet9/28
1024 FastEthernet9/25
1025 FastEthernet9/13

So, when beginning to do VLAN allocation planning, be sure to take this into account. It is best to begin your extended range VLANs at 1300 or above.