Cisco: Native VLANs

Badgerpoo · 6 Oct 2009 at 14:52

Probably not a suitable place to ask, but thought I'd give it a shot!

Can anyone think of why when two ends of a link have a native vlan mismatch (halfway through changing the native vlan) the connection should drop? I would have thought only the management interface would go down but the entire switch loses it's connection in this case. I have already configured 400 switches this way until this one, whose configuration is not abnormal.

Any ideas?

paradigm · 6 Oct 2009 at 15:00

I assume that the allowed VLANs of the trunk that has gone down include the VLAN that you have changed one of the switches "native" to?

Badgerpoo · 6 Oct 2009 at 16:59

Yeah the allowed vlan is a range excluding the new native vlan but including the old, is that a problem?

paradigm · 6 Oct 2009 at 17:06

Well yes, if your trunk at the other end isn't allowing the new vlan to communicate down that trunk, then you'll get no traffic, I think anyway.

Unless of course the trunk that you just changed includes a range of allowed vlans that are also allowed (but not native) on the other end of the trunk. In which case then your connectivity issues are bizzare.

Can you paste the config of the switch you can connect to? (or at least the relevant part of the config)

Badgerpoo · 6 Oct 2009 at 23:17

I thought the Native VLAN only related to management, the access vlans used on the switch where allowed anyway so that shouldn't change. I'll paste the relevan lines of config tomorrow to give you a better idea but it fits in with your bizarre scenario