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Webcast-Catalyst9k
New Member

VLANs on 4507

I'm coming across something weird. I'm trying to config a new VLAN on a Cisco 4507 running IOS 12.2.

I can create the VLAN just fine. I can put ports into the VLAN just fine. The ports do show up and passing some traffic. Only problem is that the VLAN itself does not come up. If I do a sho int for the VLAN, it shows that it is down and line proto is down.

In config I am making sure the int for the VLAN is not in shutdown mode.

I do see a couple of lines in the running config:

!

vlan internal allocation policy ascending

!

vlan 10,22,52,88,199,231,252

!

I am thinking this is limiting the VLANs that are in use. Should I add my new VLAN to this list?

Thanks for any info.

3 REPLIES
Cisco Employee

Re: VLANs on 4507

Do you have a port in the vlan that is up/up? If not, then the VLAN interface will not be up.

HTH,

Bobby

New Member

Re: VLANs on 4507

Yep. The ports are up/up.

On a hunch I tried looking at the VLANs that were listed to see if any weren't used anymore. I found one that wasn't in use any more, admin down, no ports attached.

Put the ports in the unused VLAN that was listed, and then the VLAN came up. Bingo!

So I think the issue is that line is specifying the allowed VLANs on the 4507.

Now my question is, if I add VLANs to the list, will it adversely affect the existing running VLANs. Will it reset them for any reason? I would think I should be able to just add to the list.

Cisco Employee

Re: VLANs on 4507

Hi,

Ah, I think i better understand the situation now.

vlan 10,22,52,88,199,231,252

!

This line defines the existing vlans on the switch. This is separate from the "Interface Vlan" which defines the layer 3 Switched Virtual Interface associated with a vlan.

So, with the vlans as created in the config above, if you were to create, for example, an interface Vlan5, it would not be up/up until you create the vlan in global config mode using the command "vlan 5" and then associating a connected port to vlan 5.

Adding a new vlan should not affect the existing running vlans. When you create a new vlan, a new instance of spanning-tree protocol will be spawned for that vlan, and the vlan will be added to the database in memory.

HTH,

Bobby

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