[c-nsp] C2691-BGP Scanning process.

[Jerimiah Cole]

dje wrote:
> BGP scanner causing high CPU burstsis quite normal. We have 7200's
> running a full feed that experienced the same spikes. 

You shouldn't see delays unless the packets are process switched, which 
is generally a bad thing.  If you ping the router iteself, I'd expect to 
see an increase in latency during the bgp scanner process, but never if 
you're pinging _through_ the router.  I have a few 7206 routers with 
full tables that don't exhibit the behavior you describe.

> The only way to reduce the CPU load is to
> reduce the number of BGP routes that the router has to process. Here's a

I don't think it will reduce the load, but it will reduce the duration 
of the high load condition.

> link to Cisco's documentation explaining why this happens:
>  
> http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00801c4f48.shtml

"Ensure that packets can follow a fast forwarding path by checking 
whether fast switching and/or CEF are enabled on the inbound and the 
outbound interfaces. Ensure that you do not see the no ip route-cache 
cef command on the interface."

Take that to heart and check the config on your 7200.

Jerimiah
Tularosa Communications