[nsp] High latency

[Streiner, Justin]

On Wed, 12 Nov 2003, Kevin wrote:

> I'm having a really strange Issue with my 7513,
> It seems like the 7513 will make the latency on any link
> Jump up to a peak of 100ms to 400ms for a few packets then settle down
> to below 1ms
> Then after a little while (30sec to 1min) it'll do the same thing,
> The cpu load when this happens is around 30%-40% (this load is constant
> during the day),
> None of the interfaces are overloaded, it happens on all the interfaces.
> Is there anything else I can do to diagnose the problem?
> It's a 7513 with an RSP4 and 12.2(14)s3.

Are you running BGP on this router?  If so, during these times of high
latency, does the "BGP Scanner" process tear up lots of CPU when you look
at a "sho proc cpu"?

If you do a "sho proc cpu hist", do you see lots of regular spikes up to
around 100%?

If so, I'll bet what you're seeing is the BGP Scanner process walking the
RIB.  If your router is heavily loaded and/or you're taking multiple full
feeds this process can eat up lots of CPU and produce the latency you're
seeing.

Running CEF won't specifically cure this problem, but it can help reduce
the amount of CPU your router spends on other tasks, particularly IP
Input.

jms