On 11/02/2012 04:52 PM, Nick Hilliard wrote:
E.g. a fully loaded 6509 with 384 ports would take ~3000 queries every several minutes to perform full port diagnostic polling, and you'd want to be doing this every couple of seconds to cause serious CPU impact. Are you doing something like full DFZ or MAC table polling?
I bet you're close toward the end there. My guess is he's carrying a large BGP feed and querying the ipRouteTable. The caveat below is for IOS 12.4(20)T but equivalent issues surely exist for CatOS: http://www.cisco.com/en/US/docs/ios/12_4t/release/notes/124TCAVS3.html#wp205... The killer in this case is not the SNMP traffic or anything resulting directly from it, but the CPU overhead from constantly re-sorting the ipRouteTable since that's generated from the FIB when CEF is enabled. Workaround is to disable CEF (heh) or configure a MIB view that excludes the ipRouteTable. This one bites an OpenNMS support customer a few times a year -- happened again just today, in fact, at a shop that just enabled topology discovery.
Also, you may want to consider moving away from CatOS, as it's now basically abandonware (or at least will formally be in Jan 2013), and hasn't even seen maintenance updates in the last 4 years.
What you said :) -jeff