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New Member

Quick vlan interface question

Hi,

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

Thanks,

J

9 REPLIES

Re: Quick vlan interface question

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.

New Member

Re: Quick vlan interface question

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

New Member

Re: Quick vlan interface question

Forgot to say it's wersion 12.2(25)

Re: Quick vlan interface question

Hi,

Unfortuantely, i've confirmed that it can't be disabled on IOS based switches, only on CatOS switches using the "autostate disable" hidden command.

http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a0080160b14.shtml#topic1

HTH,

Mohammed Mahmoud.

Re: Quick vlan interface question

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

New Member

Re: Quick vlan interface question

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).

Re: Quick vlan interface question

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.

New Member

Re: Quick vlan interface question

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.

Re: Quick vlan interface question

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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