From: Brad Fleming <bdfleming@kanren.net> Date: Fri, 17 Jul 2009 18:07:26 -0500
We don't run very much Cisco gear (none of their larger, hardware stuff) but I have a couple questions for the Cisco gurus out there...
According to this page: http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/product_dat... The Cisco WS-SUP720-3BXL can hold "1,000,000 (IPv4); 500,000 (IPv6)" route entries.
1) Does that mean a) The card can hold 1m IPv4 routes --OR-- 500K IPv6 routes or b) 1m IPv4 routes --AND-- 500K IPv6 routes?
It means that it will hole 1M IPv4 OR 500K IPv6. It means that IPv6 addresses take twice the TCAM that IPv4 routes do, so that for every IPv6 route in TCAM, you can load two fewer IPv4 routes. Worse, TCAM is partitioned with a dedicated portion for IPv4 addresses and another for IPv6 + multicast. To adjust the partitioning, you must reload the supervisor.
2) I'm assuming MPLS cuts into the number somewhere but could anyone explain it briefly?
Not really. The TCAM holds routes and the place to send packets destined for them. Since all TCAM is loaded based on flows and treated very much like MPLS, just without an external tag, the TCAM space should not be impacted. (I am NOT positive about this one, though.)
3) Do ACLs use some of these resources or do they get their own slice of memory?
Nope. They are in a different TCAM in the Sup720. They have zero impact.
That page also reports "up to 40 Gbps per slot of switching capacity; 720 Gbps aggregate bandwidth". Is the 40Gbps per slot an aggregate or full-duplex value?
I don't entirely understand the phrasing of the question, but I think you mean, do they double the numbers as router marketeers are wont to do by counting traffic in both directions? No. That is why you can drive all 4 ports of the 4x10GE card to almost the full 10G at the same time in both directions. Not quite, though. Cisco "steals" a little bandwidth on each cord for some internal signaling, so each pair of the 10GE ports is limited to about 19 GB. (I don't recall the exact number.) So they are just slightly oversubscribed. The backplane is actually a pair of 20 Gbps backplanes with the ports divided between them. On the 4x10G cards, the two top ports are on one backplane and the two bottom ones are on the other. They each have access to a full 20Gbps path less the "stolen" bandwidth. -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634 Key fingerprint:059B 2DDF 031C 9BA3 14A4 EADA 927D EBB3 987B 3751