[c-nsp] backup with STP

[lists at hojmark.org]

> True, I'm looking at it from a datacentre perspective with
> hundreds, not thousands of vlans.

Good...

As long as you don't have small, cheap switches like the Catalyst
3750 (or smaller), which will only do 128 STP instances (or less)
then you probably don't need MST...

Many of my customers use small switches, which won't do many
STPs. And even those that use more capable equipment could easily
benefit from the lower CPU utilization that you get when you only
need to calculate a couple of spanning trees.

-A