[c-nsp] network rebuild questions

[Kevin Graham]

> the soon to be smelted network consists of a pair of 6506's/SUP1's which

> each get a full BGP feed and contain customer SVI's w/HSRP. connected to
> these are 2 5500's for customer connections. all layer2.
> 
> the new core tier is a pair of 6509/(2)SUP2/(2)6516+DFC/6548/(2)SFM
> with 5 pairs of 3550's (12T's & G's) hanging off those via p2p fiber
> in a U-shape configuration for the access. eg:

Avoid this, you're probably better of with the Sup1's in this case.
The Sup2 will fall off a cliff once you blow out the 256k FIB (you cited
240k presently, which suggests you're already filtering heavily (DFZ from
our PoV is ~290-30k presently). For all of its drawbacks, the Sup1 will
degrade far more gracefully.

Also skip the SFM's. If you're OK w/ constrained FIB, I would imagine
original Sup720's aren't that much more than 2xSFM and 2xSup2. If you have
to, go w/ a single sup per switch and later on buy a pair of something newer
and pair those two together.

You also save 2 slots per chassis (w/ the possibility of using 67xx cards in
the future), but most importantly stay on future code (Sup2 is dead as of 
SXF but all 720's run the same software).

You'd be much, much better off to try and score a pair of used NPE-G1's,
which will eliminate the need for the 2600XM RR's, keep you on a well-
supported platform, allow you to take full tables and probably save enough
that you could work in a 3rd one or perhaps a 3550-12.