On Fri, Jul 17, 2009 at 06:07:26PM -0500, Brad Fleming wrote:
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?
Woops, I missed this question. On CEF720 (aka the cards numbered 67xx that claim to be 40G/slot) what you actually have are two 20G fabric channels to each slot. The fabric channels are full duplex, so you could have 40G per slot coming in and out of the same card, and Cisco double-counts the packets (in and out) to get 9 fabric slots * 40G * 2 = 720. On 6704 cards, ports 1 and 2 are in one fabric channel, ports 3 and 4 are in another. On 6748 cards, even ports are in one channel and odd ports are in another. On 6724 cards, there is only one 20G fabric channel. Of course there are literally a list of caveats a mile long to explain why you won't actually get anywhere near 720G out of the box, but the big one you want to be careful of is sending traffic within the same fabric channel (i.e. from port 1 to port 2 on a 6704). This will cause a bottleneck at around 7-8G, with lots of input or output drops. You can also view the fabric utilization with "show platform hardware capacity fabric", though you should keep in mind that these counters are about as accurate as the others on this platform (wild variations at best). -- Richard A Steenbergen <ras@e-gerbil.net> http://www.e-gerbil.net/ras GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)