[c-nsp] purposefully mismatching native vlans

[Andrew Fort]

Mark Brochu wrote:
> I feel that disabling spanning tree on that vlan is justifiable.  I can 
> also prevent the log spam by disabling cdp v2 on the other ends.  I'm 
> wondering if there are any other possible caveats I may run into. 
> Looking forward to your input!
>
> Mark Brochu
> Network Analyst
> University of Hartford
>   

This hack has worked for me in the past, though I last used it on malbiu 
2924 switches.  Simple rule: Avoid loops.  The main problem you'll get 
if someone closes a loop: CAM tables that see both "1" and "1841" will 
think they're different VLANs and will happily populate the same MAC 
address, on different ports, in those "different" VLANs, so you won't 
even get detection of "mac moves" if your hardware supports that and 
you'd configured it.

VLAN translation is available on some kit (may be worth looking at 
vendors other than cisco here for a point solution linking these two 
networks), so given the likelyhood of loop being formed and how much 
you'd like to not have your ops staff days' ruined, perhaps this is 
worth considering further.

-andrew