Add vlan on a trunk

Unanswered Question
Sep 3rd, 2008

Hello

If my trunk is in use between two switch, if I use the add command to add another vlan allowed in the trunk, Is there a cutoff network?

I have this problem too.
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Calin Chiorean Wed, 09/03/2008 - 04:24

Hello Claude!

Use:

"switchport trunk allowed vlan add x"

and you will have no outage there.

Good luck!

Cheers,

Calin

claude1968 Wed, 09/03/2008 - 04:41

Thanks a lot.

The addition "add" of a vlan in a trunk does not cut the networking of others vlan allowed in the trunk. Is Cisco has documented this because I found no documentation about that?

francisco_1 Wed, 09/03/2008 - 05:02

claude1968,

From what i interpreted, your question is "if I use the add command to add another vlan allowed in the trunk, Is there a cutoff network?

If you dont have the switchport trunk allowed vlan [vlan-id]command already enable on your trunk and you add that command, you will block all other vlans except the vlan you are allowing.

If you already have the switchport trunk allowed vlan [vlan-id] command and add another vlan then yes you will not block any other vlan in the list.

Francisco.

francisco_1 Wed, 09/03/2008 - 04:25

by default, all vlans allowed on the trunk link so yes you will because you are limiting the vlan allowed on the trunk. only the vlan you allowed with the "switchport trunk allowed vlan [vlan-id]" command will work on the trunk link.

use the "switchport trunk allowed vlan [vlan-id]" comamnd on both switches to permit the vlans on the trunk link

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