[c-nsp] pvst and mst

[David J. Hughes]

If you are running RPVST with some legacy PVST you can still configure 
all your normal PVST tweaks to get the same as you would in a pure 
legacy environment (uplink fast etc etc).  We have foundry L4/L7 
switches that I doubt will even understand RPVST so we'll always have 
some legacy kit regardless of upgrade strategy.


David
...


On 18/03/2005, at 7:35 AM, Matt Buford wrote:

> Although this works for a migration, I wouldn't recommend this as a 
> long-term solution.
>
> A big catch is that when a non-edge port changes state, spanning tree 
> on all ports on the same VLAN (or all VLANs if trunked) on the same 
> switch are reset.  For your RPVST neighbors, reconvergence is quick 
> and it is no big deal.  For your PVST neighbors, you get a nice big 
> outage.
>
> We had a 6500 with trunked RPVST backbone links, a number of servers, 
> and a PVST link down to a couple old legacy 3500XL's that can not 
> speak RPVST. Every time someone rebooted one of the servers, the link 
> to our old PVST switches would reset spanning tree, giving us a nice 
> 30-45 second outage. Setting all server ports to portfast/edge avoids 
> the issue for the server ports, however if one of our RPVST backbone 
> links flaps the PVST ports still take a hit.
>
> According to Cisco, this is not a bug, but is the normal behavior.
>
> ----- Original Message ----- From: "David J. Hughes" 
> <bambi at hughes.com.au>
> To: "Alexander Koch" <efraim at clues.de>
> Cc: <cisco-nsp at puck.nether.net>
> Sent: Thursday, March 17, 2005 8:24 AM
> Subject: Re: [c-nsp] pvst and mst
>
>
>>
>> From our experience, dodge MST.  Rapid PVST can happily co-exist with
>> "standard" PVST so your legacy Cisco switches will be well supported.
>> Migration from PVST to RPVST is a much more pleasant experience (and a
>> lot easier to revert if it all goes pear shaped).
>>
>>
>> David
>> ...
>>
>>
>> On 17/03/2005, at 11:16 PM, Alexander Koch wrote:
>>
>>> Hello folks,
>>>
>>> hopefully someone can clue me in that knows the whole story.
>>>
>>> We have a mixture of 3508 and 2950 Cisco switches in some
>>> sports of our network and the number of VLANs increased a
>>> lot lately. Now, the 3508 cannot do MST or rapid-pvst if I
>>> am not mistaken. That being said I have basically two Q's:
>>>
>>> 1. Can psvt and mst co- exist? I get told they can, it has
>>> to do with setting all ports (default) to portfast except
>>> the trunks, and then mst and pvst can live fine with each
>>> other. Obviously we need that thing to work with the 3508.
>>>
>>> 2. Is there a sane way to switch from pvst to mst, without
>>> losing management completely? ,-) It probably is related
>>> to the 1st question, yes, but how does one migrate from a
>>> to b here the easiest way?
>>
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