[c-nsp] Disabling PVST+ in mixed vendor network

[j.vaningenschenau at utwente.nl]

>> By the way, the first time this happened it wasn't following a
>> reload or crash of the Cat6k. If I remember correctly, it coincided
>> with someone connecting a Cisco 3020 blade switch, which we expected
>> to be the cause. I think that incident led to us blocking
>> 01000c-cccccd wherever we can. Still, I don't understand why it
>> happens and how we can completely avoid it.
> 
> We don't use MST, so take this with a pinch of salt...
> 
> During my reading, I seem to recall that Cisco devices perform some
> kind 
> of PVST->MST integration at ports at the "edge" of an MST cloud:
> 
>
http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/con
figuration/guide/spantree.html#wp1098679

Since all our HP's connected to the Cisco's are running RSTP (and the
Cisco's MST), I guess each Cisco port leading to a HP switch is
considered a boundary port.

 
> Is this your issue?
> 
>
http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/con
figuration/guide/stp_enha.html#wp1054786

Yes, that's what happens... so we could also enable PVST Simulation
again, hoping that receiving a PVST+ BPDU doesn't result in a "peer
inconsistent" state. But still, I'd prefer killing this protocol
entirely. It's
 

> The problem is that if you've got non-Cisco switches downstream which
> are a) MST enabled but b) still pass PVST PDUs, then you're going to
> see "PVST peer inconsistent" on the port on the Cisco, not at the
> edge of the network.

Right, that's what happens. And what I'm trying to achieve is that the
Cisco Cat6k completely *ignores* these proprietary PVST+ frames... Maybe
it's me, but I just don't understand why I can't just disable all PVST+
"features". Other proprietary protocols such as DTP can also be turned
off (at least at port level), so why not PVST+?

But let's not go on a complete rant here... perhaps enabling PVST
Simulation again will prevent the Cisco ports to go blocking; I'll test
that in a service window.

Thanks again for your comments and insights.


Regards,

Jeroen van Ingen
ICT Service Centre
University of Twente, P.O.Box 217, 7500 AE Enschede, The Netherlands