Nick,
I run RANCID on my SP network and I too see the high CPU spikes. Mine
actually clock in at 100% (high enough that it makes my 1m average
register 80% on some devices via sh pr cpu his (which means that it's
actually between 80 and 89%)). I have a couple devices in particular
that it hits hard. One is a 7206 (G1) with almost 15,000 lines of
config. That other is a 3660 with over 18,000 lines of config. I've
never had any trouble though and I poll my devices hourly.
I'm not aware of any way of throttling the access that VTYs have to the
control-plane. In general I think the best approach is to make sure
that your IOS device is well-configured and tuned with performance in
mind.
http://www.cisco.com/univercd/cc/td/doc/product/software/ios113ed/cs/csprtf/csprtf4/csperfrm.htm
For example, have you configured your routers to use the Nagle
algorithm? I'd highly recommend looking into it.
http://www.google.com/search?hl=en&q=service+nagle&btnG=Google+Search
The first couple of hits (especially the Cisco Press one) give you good
info.
Justin
Nick Davey wrote:
Hi All,
I've deployed rancid on a fairly large metro network, and am seeing some
pretty high CPU averages. When RANCID runs the CPU's on a large number of
our boxes spike to about 95% for several seconds. Although they have never
hit 100%, or caused any issues (dropped OSPF hello's, stp bpdu's) I'm
concerned that this could happen under the right combination of events this
could result is dropped OSPF neighbor adjacency's or other badness.
I've tried to replicate the high CPU issue by pasting the commands in
manually however I haven't come anywhere close to the 95% I'm seeing when
RANCID runs them. I'm assuming this is just the frequency at which the
commands are run. Does anyone have any experience with this or any insight
they can provide?
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