[c-nsp] BGP scanner taking up CPU

[Oliver Boehmer (oboehmer)]

Joris de Mooij <> wrote on Friday, August 11, 2006 2:11 PM:

> Hi all,
> 
> We have a 6506 with Sup720-MSFC2 running IOS 12.2(18)SXD5. This router
> holds the entire internet BGP table. Now we are suspecting the BGP
> scanner process for causing temporary high CPU loads. Because this
> process runs with a high priority, exec commands, pings and snmp seem
> no to get through anymore. When using the vty exec, output seem to
> stall for 1 to 3 seconds at least every minute.

BGP Scanner is a low-priority process (check "show proc <pid>"), it
should not have that adverse effects. Maybe something else is going on.
 
> Now there is a command to tune how long a single process can claim the
> cpu. This timer can be tuned with the process-max-time command. The
> process-max-time is default 200 ms (and this is also the max). It can
> be tuned down 20 ms.
> 
> Can anyone tell me if lowering this value could have a positive effect
> on the CPU usage of the BGP scanner process?

No, and we recommend not to tune the scheduler unless you know about the
side-effects.

> One other thing that may be beneficial is to use next-hop
> address-tracking (NHT). Available in IOS 12.3(14)T and up. I am not
> sure if this feature is supported on 65xx sup720 (software advisor
> claims it is not) and upgrading this router has a big impact. Anyone
> ever used this feature on a 65xx sup720 and know of its impact on the
> BGP scanner? 

BGP scanner will still be around, but will no longer need to scan
everything and uses much lower CPU value. NHT is available in 12.2(33)SR
for the 7600..

best open a TAC case to find out why the router responds so slowly..

	oli