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New Member

show vlan output

When doing a "sh vlan" on our 3750 (12.2 20 SE), I have noticed that the information displayed under the ports column is not consist with the configuration. The VLAN membership information seems to be out of date.


Re: show vlan output

please provide the output if you can so we can view and see what you're talking about.

identify the information you see as 'out-of-date'.

also, is this the only switch in your environment? are you using VTP in a multi switch environment? if so, did you do a 'show vlan' from a VTP client or the VTP server?

New Member

Re: show vlan output

OK, not using VTP. The 3750 is part of a switch stack, 3 x 3750G-24TS.

See the cut down output:

VLAN Name Status Ports

---- -------------------------------- --------- -------------------------------

106 NLB-Network4 active

Yet VLAN 106 is added to the allowed vlan list on many ports includingthe folowing:

interface GigabitEthernet1/0/11

switchport access vlan 904

switchport trunk encapsulation dot1q

switchport trunk native vlan 904

switchport trunk allowed vlan 104,106,154

switchport mode trunk

no cdp enable

spanning-tree portfast

Hope this helps.


Re: show vlan output

Not really sure what you are trying to say here . It looks like you have a layer 2 vlan created and it is allowed across the trunks , don't see anything wrong with this . If you are saying vlan 106 does not show up on any ports then that is just a manual thing , there is no automation in the process . You would have to disallow the trunk across the vlans and then delete vlan 106 manually . All your first display is telling you is that no ports are currently active in vlan 106 .

New Member

Re: show vlan output

I have read the command reference for this IOS release and it states that the Ports column shows ports that belong to the VLAN. As I have stated above there are no ports under this column when I do "sh vlan" for the VLAN in question yet I have many ports that belong to this vlan, including the provided example. I was just wondering why this was happening.


Re: show vlan output

There is no problem or reason why you don't see any port next to vlan 106 in the output of show vlan. If you modify the port to switcport access vlan 106 you will see that the port will be listed in the output of show vlan brief. If you just allow the vlan 106 traffic it you will not see the port as a member of the allowed vlan.

I hope you catch my point.



Please rate me if I helped.

Re: show vlan output


the output from "show vlan" will not show a port, when the port is a trunk. In your configuration the access VLAN is 904 and additionally the port is configured as trunk port with allowed VLANs including 106.

This does not mean, that the port belongs to VLAN 106. In fact, a trunk does not belong to any specific VLAN, but allows to transport VLAN traffic to another switch (or other trunking device).

So it is quite normal what you observed. It reflects your configuration. If this is not what you intend to achieve, let us know and we will help you to adjust your config to the desired result.

Hope this helps! Please rate all posts.

Regards, Martin