3550 VLAN Interfaces Problem

[tsmarcyes]

I was setting up two VLAN interfaces for my 3550. I had two VLAN interfaces. One for VLAN 10 and one for VLAN 15. After configuring each VLAN Interface, VLAN 15 was down and wouldnt come up. VLAN 10 was up however. After issuing the no shutdown command for VLAN 15, it said VLAN 15 is not shutdown, but, when i checked the interface again, the VLAN interface was up. Now, I would think, if I had to do the no shutdown command on VLAN 15, why didnt I have to do that on the VLAN 10 interface? With switches, is the first VLAN interface automatically always up and all later VLAN interfaces automatically shut down.

[timothykerr]

Good afternoon,

The VLAN interface will continue to show down until it is applied to an interface (such as FastEthernet 2/10). Once the VLAN is applied to an interface the VLAN should show up and up.

HTH

[tsmarcyes]

Ok, Im not quite sure on what you mean. Do you mean it will show down, down until there is a port with the VLAN assigned? If that is what you mean, that wasnt the problem. Like I said, when I issued the show ip int VLAN command, it showed down, down. I then went in the interface, issued the no shutdown command, it said the VLAN interface was not shutdown, went back and issued the show ip int VLAN command, and it was up, up.

[timothykerr]

Could you please send on an exceprt from your running config? To include the configuration of all of your interfaces. Thanks

[chapmanwong]

For any port interfaces you have assigned to VLAN15 may need to have a device physically plugged in to have the vlan show the up status.

[rseiler]

A 'feature' of all the newer Catalyst switches and newer IOS is that the logical VLAN interface will remain down until a port in that VLAN is up.

The VTP config/status can also complicate this as a VTP client doesn't have the VLANs that the IOS config actually has because the VTP client hasn't learned the VLANs yet. In other words, the switch is in a state in which the IOS config puts a port in a VLAN that doesn't yet exist because VTP hasn't downloaded the VLAN database.

Keep in mind that VTP requires an operating trunk and if it is 802.1q then the native VLANs must match (so a native VLAN other than 1 will not work if the VLAN database hasn't been dowloaded by VTP or has been corrupted).

Not that you are running into the VTP issue, but in the effort of full disclosure...

Hope that helps...