Calculating the Current Packets Per Second

[Dominique Demore]

Is there a method of calculating the current pps on a router. I am starting to suspect that one of my routers is reaching the max pps supported by the platform.

Thanks.

-- Dominique

[7rbowenii]

D-

It would probably be easier to figure out your average packet size (with a sniffer or probe) and then calculate the theoretical upper limit. You could also do a very loose guess if you take the max pps and multiply it by the # of bits and see how this compares to your routers utilization oveer a link or CPU. Other processes also can take a toll on how much CPU is available for processing traffic. Not to mention not having features like CEF turned on.

-Bo

[Dominique Demore]

Thanks, I will get the avg packet size on Monday.

IP cef is enable.

What I am seeing is the avg cpu is around 60-70% on the 5minute interval with mrtg.

I do see spikes of 100% every once in a while. There is an average 25Mbit/sec going through the router. I don't know if that is too much for a 2621xm.

Thanks.

-- Dominique

[7rbowenii]

Platform Throughput (max, fast-switching)

2610-12 15K packets per second (pps)

2620/21 25K pps

2650/51 37K pps

2610/11XM 20K pps

2620/21XM 30K pps

2650/51XM 40K pps

2691 70K pps

According to this info, at 64B packets the throughput would be 12.8 Mbits at 1516B it would be

181 Mbits.

So, packet size * 8 (bit conversion) * max pps = throughput.

This doesn't give you any definitive answers, but if you are pushing a large percentage of small packets, then CPU uts could easily be explained.

Heres a link with some goodies...

http://www.cisco.com/en/US/customer/products/hw/routers/ps259/products_tech_note09186a0080094e92.shtml#cef_switching

HTH

-Bo

[Kevin Dorrell]

It also depends on the configuration. Features like debug, access-lists with logging, and some IP accounting features, can cause packets to be process switched rather than CEFed. This is known as "punting", and here is a document to read if you suspect this might be happening:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1828/products_tech_note09186a00801e1e46.shtml

In short, try show interface stats and check that it really is doing CEF.

Kevin Dorrell

Luxembourg