Quick vlan interface question

Unanswered Question
Jun 22nd, 2007

Hi,

Is there any way to keep a vlan interface up without having any active physical ports in the vlan?

Thanks,

J

I have this problem too.
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mohammedmahmoud Fri, 06/22/2007 - 03:43

Hi,

Try disabling the autostate feature you can accomplish this by using "autostate disable" (its a hidden command), the autostate feature is enabled by default, but i guess that on IOS based switches, this feature cannot be disabled.

HTH,

Mohammed Mahmoud.

jigsaw2026 Fri, 06/22/2007 - 03:55

Hi Mohammed,

Thanks for your response - I'm pretty sure that's what I need to do, but I can't find the correct command to use. Do you know what it would be on a c3750 please?

Thank you,

J

MUHAMMAD SHAHEEN Fri, 06/22/2007 - 08:07

Hi,

If you only have a single switch then it is not possible, or at least i don't know.

But If you have 2 switches linked via Trunk then your VLAN will be up regardless of any port assignment. If you have a Router on the Stick setup then change the switchport which connects to that router to be a trunk. and configure Eth port on the router with sub-interfaces. This should help.

Hope this helps !!

Shaheen

jigsaw2026 Fri, 06/22/2007 - 08:52

Thanks for your reply - there is actually l3 routing between switches so no trunking. I want this vlan to reside purely on one sight (where only the one switch is).

mohammedmahmoud Sat, 06/23/2007 - 00:28

Hi,

The answer would be that you need at least one port in the VLAN in the connected state or there should be a trunk in the connected state, IMHO unfortunately no way around.

HTH,

Mohammed Mahmoud.

guillaume.labarthe Sat, 06/23/2007 - 01:31

In my opinion, an interface Vlan remains up as long as you do not shut it down.

Do you mean that it goes sometimes down without any reason ?

You can also use routed interface, that would avoid you to set a port in that Vlan.

mohammedmahmoud Mon, 06/25/2007 - 04:51

Hi Guillaume,

If the SVI interface is created but the VLAN is not configured on the switch the SVI interface will be down/down, if the VLAN is created on the switch but no port assigned to this VLAN is UP/UP (or an UP/UP trunk) the SVI stays up/down.

HTH,

Mohammed Mahmoud.

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