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New Member

Could SVI be up/down with vlan not in database?

Hello,

I have a Cisco 3750 switch with IOS 12.2(50)SE2.

I have an SVI for a vlan 20 which is currently in up/down state. I have been told that it was working until last month. When I do a show vlan or show vlan id, I do not see the vlan 20 in the database. The physical port associated with the vlan 20 is a trunk port. It allows all vlans but I do not see vlan 20 under it.

There are two questions:

1. Should adding the vlan 20 to the database fix the issue?

2. It was all working before and it is hard to imagine that someone went and removed vlan 20 from the database. There was no configuration change. Just a log that the int vlan 20 chnaged to down. What could have triggered this?

Thanks,

Nadeem         

6 REPLIES
Hall of Fame Super Blue

Could SVI be up/down with vlan not in database?

Nadeem

1) There should be a vlan 20 in the vlan database even if there are no ports allocated into it.

2) No idea. Are you running VTP server/client or VTP transparent ?

Jon

Purple

Could SVI be up/down with vlan not in database?

  If the vlan is not  shown with the 2 commands you mention then it's not in the database and the SVI  will not go up/up . If vlan 20 is actually needed  which can't be too important if it's been down a month then create  the L2 vlan for the database .

New Member

Could SVI be up/down with vlan not in database?

Thanks for the help. I added the vlan and it fixed the problem.

Still do not know what caused it to begin with.

Jon,

It is running VTP server mode.

Thanks again,

Nadeem

Bronze

Could SVI be up/down with vlan not in database?

Hello Nadeem,

The vlan down state will be triggered when there are not interfaces local to the switch for that vlan that are up. So if

the only vlan interfaces was the trunk this would cause the vlan state to go down.

Remember that for the VLAN interface to be up, we need to have three basic elements:

The layer 3 interface vlan , which is the virtual VLAN that is created with an ip address, the regular VLAN at layer 2  with the same ID which you assign to a port, and third a device connected and assigned to the VLAN.

Haihua

Hall of Fame Super Blue

Re: Could SVI be up/down with vlan not in database?

Haihua

         

The vlan down state will be triggered when there are not interfaces local to the switch for that vlan that are up. So if the only vlan interfaces was the trunk this would cause the vlan state to go down.

I suspect this may be a terminology thing but the above is misleading. You do not need interfaces on the switch assigned into that vlan for the SVI to be up/up. As long as the vlan is in the vlan database then either -

1) a trunk port which allowed that vlan and was up/up would bring the SVI to up/up

or

2) a port allocated into that vlan which is up/up would bring the SVI to up/up

Jon

Bronze

Could SVI be up/down with vlan not in database?

Thanks Jon,

Maybe I did not made myself clear but you are correct the above options are the faultless one.

Haihua

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