[c-nsp] Adding vlan to port-channel trunk causes port-channel to flap

[Jeff Kell]

On 1/7/2010 7:06 PM, Tom Lanyon wrote:
> I've run into the same problem on our 3750Gs and 3750Es (running 12.2(46)SE) with no solution so far.
>
> The log on our switches indicates that it's due to the config for the Port-Channel being different than the underlying Gix/y/z interfaces, which is not allowed, so it shuts the etherchannel down. I tried to work around this by adding the VLAN to all ports at once, eg:
> 	conf t
> 	int ran gi1/0/1, gi1/0/2, po1
> 	sw trunk allowed vlan add 400
>    

For vlan changes on port channels, I've always used just the 
port-channel configuration (e.g., int portch1) and applying vlan 
adjustments there, which IOS appears to propagate to the active member 
configurations, provided of course the port channel is up.  We do this 
"a lot" across a broad range of Catalysts (no MEs though) with no issues.

If you change an individual member characteristic, it will indeed break 
the interfaces out of the port-channel and bounce.

Jeff