[c-nsp] Replacing a 7206VXR w/ NPE-G1 with Sup720-3BXL w/ WS-X6408A-GBIC

Wed Jun 29 11:49:12 EDT 2011

Thanks. I had (perhaps foolishly) assumed that moving from an NPE-G1 to a 
Sup720-3BXL-based platform would represent an upgrade from the 7206VXR (as 
well as having the advantage of bringing our Internet BGP tier in-line 
with the rest of our core network from a hardware perspective).

When comparing the NPE-G1 to a Sup720-3BXL for the purposes of being an 
internet-facing BGP router am I actually proposing a backwards step?

From:
Peter Rathlev <peter at rathlev.dk>
To:
Matthew.Coleman-Hamilton at servicebirmingham.co.uk
Cc:
cisco-nsp at puck.nether.net
Date:
29/06/2011 16:38
Subject:
Re: [c-nsp] Replacing a 7206VXR w/ NPE-G1 with Sup720-3BXL w/ 
WS-X6408A-GBIC

On Wed, 2011-06-29 at 16:14 +0100, 
Matthew.Coleman-Hamilton at servicebirmingham.co.uk wrote:
> Can anyone confirm exactly how traffic will be forwarded by the 
> Sup720-3BXL with a WS-X6408A-GBIC in the chassis?

The PFC3B on the supervisor will make the forwarding decisions.
Throughput is limited by the 32 Gb/s (simplex) bus and the 15 Mpps per
system as you mention.

You should also look into buffer sizes and the card's ability to handle
bursts. I don't know the 6408 card, but we've used 6516 (CEF256) cards
with success for many years.

You should also beware that the Sup720 route processor is quite weak
compared to a NPE-G1, and things like BGP processing might take somewhat
longer than usual.

This white-paper explains the forwarding architecture quite well, though
it has little information on classic bus forwarding:
http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/prod_white_paper0900aecd80673385.html

http://tinyurl.com/2w7yu3 (same link)

If you try searching for "BRKARC-3465.pdf" in your favorite search
engine you could find a presentation from a breakout session that
explains things in more detail. I'm not sure it's an official document,
so I'd rater not link directly to anthing. But it's worth a read.

-- 
Peter