[c-nsp] backup with STP

[David J. Hughes]

On 30/09/2005, at 8:30 AM, Andrew Fort wrote:
> Agreed in a network running PVST+ it would've been far simpler to
> transition to RPVST+, and harder to transition to MSTP/RSTP.  Such an
> original design choice of PVST+ may have been more based upon it
> being the only ball-game in town to load-balance, at the time.

We rolled out MST a couple of years ago and had major issues.  No doubt 
we were hitting IOS bugs at the time but still, outages tend to leave a 
bad taste in your mouth.

In our environment we don't need to group vlans to limit the number of 
STP instances.  For that reason alone we don't need the added 
complexity of MST (multiple reagions, IST / CIST / legacy interaction 
etc).  It's not hard for the guys at the "coal face" to understand a 
PVST based STP configuration (being it normal or rapid).  There are a 
lot more corner cases to understand with MST.  And, putting MST 
vlan-to-instance configuration on every switch in the network just 
makes the configs look ugly ;-)

I guess my point is that PVST or RPVST are very easy to deploy and 
understand.  There's a lot more to understand with MST and unless you 
are like Steinar and need 4,000+ vlans in a single layer 2 domain, the 
complexity isn't warranted.  Horses for courses as they say.


David
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