GSRs are useless if you are doing any kind of aggregation. Their traffic
shaping abilities are embarrassing.
Historically yes, but no longer. The latest line of GSR cards now
give them much greater capability in this area even though it was
never designed as an access box.
7500 is the classic aggregator. They do the job quite well, actually.
Based on cost right now, I would take 10 7500s over 1 7600 anyday.
If you are just aggregating E1/T1 then I'd agree, but the minute you need
DS-3/E3/STM-1/ATM/100BaseT/Gige aggregation then the 7600 is a far better
choice cost wise, if only the code on it worked. The feature set for the
7600 and the roadmap is very impressive but Cisco need to spend a large
part of time a: fixing the bugs in the code and b: training their people
how this box works.
For transit, though, I would use a Juniper - hands down. Cisco has to get
their $hit together in terms of software stability.... one would hope it
would get more stable over time.... but alas no.
"transit" ? In my view the software on the GSR is very stable, in fact
probably one of the most stable parts of the IOS family. I can count on one
hand the number of real bugs we have for the GSR in the last 3-4 years, and
two of them were security related. [which as I understand it Juniper
is not ammune to either]. There are issues with the early engine 0 and
engine 1 cards on the GSR so beware if buying second user cards.
Also I would not underestimate the effort of going multivendor for core
and access devices. There are alot of issues other than just cost
when going multivendor.