[nsp] 5 9's infrastructure, stateful failover

[rpcbind at speakeasy.net]

> yes, this used to be true until last year. there is a magic little
> thingie out there, called rapid spaning tree protocol
> 
> deploy it well and it also is magic in production, of course :)

Support is a bit disorienting though -- cat4000-sup3/4 support was recently 
rolled into 12.1E and while I picked up 'PVRST+' on the cat6000's, got to go 
back to 12.1EW for it on the 4000's. Wasn't reading release notes closely, 
but it was a bit of a disappointment after last week's 'free' upgrade 
excuse...