Justin Shore wrote:
Does anyone know of a good article, table or chart that compares the
various T3 and T1 PA options? I've found a variety of docs but nothing
of them giving a clear and concise list of differences between the PAs
(features, chassis support, NPE support, etc).
PA-T3
PA-T3+
PA-8T
These PAs, without -MC in the model, deal with their ports as a single
interface. In other words, if you insert a PA-8T into a 7206 in slot 6,
I'd anticipate Serial6/0 through Serial6/7 showing up in your config.
PA-MC-8DSX1
PA-MC-8T1
PA-MCX-8TE1-M
PA-MC-T3
PA-MC-T3+
PA-MC-T3-EC
These PAs, with -MC in the model, are channelized ("Multi Channel"), and
can (must?) deal with their ports as multiple channel groupings, each of
which presents itself as a Serial interface once configured.
I've found all sorts of docs on the DS3s but again nothing terribly
concise or a clear-cut comparison between the different models. For
example I know that the PA-MC-T3-EC can do MLPPP in hardware but not on
the PA-MC-T3+.
Correct. The PA-MC-T3+ depends on the system CPU for MLPPP. AFAIK, the
system CPU still handles the basic PPP duties, thereby negating some of
the redundancy features that you'd hope/expect in a 7500.
We bought the EC model for our T1 delivery service on 7200s (G2) but is
it really needed? A fully-loaded 7200 with PA-MC-2T3-EC modules only
puts 12 DS3s in a chassis. At full line-rate that's just shy of the
throughput limit on a G1 and still half that of our G2. Now I'm sure if
all our DS1s were in MLPPP bundles that this would certainly add load to
the CPU but we're 25/75 CC DS1s and MLPPP bundles at this point. I
could probably buy used PA-MC-T3 cards and do what I need if only I knew
what the feature differences were.
We converted a POP from 7507/RSP4/VIP2-50s to 7206/NPE-225, with one
PA-MC-2T3+. One T3 had fractional T1s on it (about 3/4 full), the other
T3 had full T1s on it (about 3/4 full), with three MLPPP groups totaling
about 10 T1s. We saw CPU around 20-35%, which had me a little worried.
It's held steady in proportion to MLPPP traffic, so I've been OK. I
had an internal policy to limit 7206/7507s to no more than two
PA-MC-2T3, for stability and config size, which should have kept the
7206 CPU down sufficiently for us.
One thing I need to know is on which T1 PAs is MLPPP supported. I need
to know if MPLS (core-facing) would be supported on a bundle of T1s. I
need to know which DS3 modules support core-facing MPLS.
MLPPP should be supported with most IOS, as long as you keep the bundle
on a single PA.
Core-facing MPLS on MLPPP is going to be a problem. You may want to
search the archives for a post from Rodney Dunn on this particular
topic. He mentioned that it definitely wasn't supported under
12.0(27)S, and I knew we were running it on that 12.0(27)S5. I checked
my routers, and found that VIP CPU on the relevant boxes was pegged at
99% since a recent topology change, and was impacting packet forwarding
heavily over that path. That link was going away anyway, so we
torpedoed it that night.
pt
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