Solved: VLAN id's 1025 - 1102

TIM POTTICARY · ‎11-16-2007

I'm trying to create a number of extended vlan id's for LAN on a couple 6513 with sup 720's, I seem not to be able to create vlan's with id's 1025 - 1102 I get the following error message.

Switch(config-vlan)#exi

%Failed to commit extended VLAN(s) changes.

I have no problems with vlan's > 1103

If I issue a show vlan internal usage

I get the following out put

1024 GigabitEthernet6/11.1024

1026 IPv6 Multicast Egress multicast

1027 GigabitEthernet4/1

1028 GigabitEthernet4/2

1029 GigabitEthernet4/3

1030 GigabitEthernet4/4

1031 GigabitEthernet4/5

1032 GigabitEthernet4/6

1033 GigabitEthernet4/7

1034 GigabitEthernet4/8

1035 GigabitEthernet4/9

However I have not configured these VLANs and if you do a show vlan they do not exist

Tim

Kevin Dorrell · ‎11-16-2007

These are nominal VLANs that have been created to represent your layer-3 ports (no switchport). It looks like it has reserved 78 numbers for that use, but I'm not sure why. Do you have 78 ports on the box or something?

I believe it is possible to modify the algorithm it uses to allocate these nominal VLANs, vlan internal allocation policy, but I admit I have never tried it.

Kevin Dorrell

Luxembourg

View solution in original post

Jon Marshall · ‎11-16-2007

Hi Tim

Kevin is correct, these internal vlans are used by the switch itself to represent among other things routed ports. They will not show up in a "sh vlan" and they cannot have ports assigned into them by the administrator.

You can change the way the 6500 allocates vlans so instead of starting at 1006 and going up it starts at 4094 and goes down. See attached link for more details.

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/vlans.html#wp1038695

If you want to be sure of no conflict just start at the other end of the range so if your vlan internal policy is ascending (the default ) start at vlan 4094 and work backwards and if it is descending start at 1006 and work upwards.

HTH

Jon