Old VLAN showing up again!

[damesac]

In the recent past, I had deleted a given vlan from our VTP server thus removing the vlan from all client switches in the network.

Last week I did an upgrade to the IOS on one of our access switches and lost connectivity with it upon the reload. A physical inspection of the access switch showed there to be no link light....but consoling in showed the new IOS came up fine and the configuration was not corrupted.

Looking at the core switched also showed no link light to that access switch. Telnetting into the core switch and looking at that port showed that the port had been associated with that previously mentioned vlan that had been deleted awhile back.

Upon resetting the port on the access switch to the proper vlan membership restored connectivity to the access switch.

My question is how, by reloading the access switch, did it try and negotiate a vlan membership of a vlan that was non-existant with the core and/or what could have caused the core to 'misconfigure' itself like this?

"Be the packet."

 

[pmesjar]

If you have associated the port with VLAN using "switchport access vlan", then the port will be still in that vlan even after you have deleted it and then reloaded the switch.

Peter Mesjar
CCNP, A+ certified
pmesjar@centrum.sk

"The only true wisdom is in knowing you know nothing.

 

[damesac]

Upon the reviewal of some older configs, I noticed that the 'previously deleted' vlan had always been configured to the port on the core switch. It didn't give any errors until the reload of the access switch because when the two switches attempted to negotiate the trunk link, the access switch tried to use a given vlan (valid) and the core tried to use the vlan that had previously been deleted (now invalid). When the trunk is negotiated, the native vlans of each port don't have to match (might cause some other issues), but they do have to be valid and since the vlan that the core switch tried to use was not valid, the trunk link was never negotiated thus breaking connectivity to the access switch. My bad, I should have immediately checked the old configs and I would have seen this. Thanks for the reply though!

"Be the packet."