[c-nsp] Brief CPU spikes on 6500 Sup 720

[JC Cockburn]

Hi Phil,
I had a problem like this last year on 6500's.
It was related to bug: CSCsk23521
Basically a server in our datacenter used multicast addresses in the range
allocated for BPDU's, and this just killed the SP (100% CPU...).

If you do a "remote command switch sh proc cpu" on the 6500 you can see if
the SP CPU is under fire...

Cheers
JC

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Phil Mayers
Sent: Wednesday, July 14, 2010 1:41 PM
To: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] Brief CPU spikes on 6500 Sup 720

On 14/07/10 11:30, Aaron Riemer wrote:
> Hi Group,
>
>
>
> We are having trouble with unicast flooding on a particular VLAN and
> associated ports and as a result brief spikes in CPU usage on one of our
> 6509 core switches.
>
>
>
> ARP and MAC timeouts are set to default and we haven't had problems with
> this in the past. The problem is I believe this is causing brief 100%
spikes
> within the SP or RP and as a result brief connectivity outages.

Which is it? SP or RP?

>
>
>
> We have narrowed down the source of the unicast flooding but we need to
know
> why it is occurring.

Rather more info required I think.

  * IOS version
  * Config of ports & SVIs in question
  * Nature of downstream devices (if any)
  * spanning tree config (if any)
  * rough idea of the size of the ARP & MAC tables
  * Any MLS rate-limit or CoPP config
  * Nature of the source of the unicast-flooded traffic
  * Any possibility of loops in the network?

> Has anyone experienced this in the past? Could unicast flooding over
> multiple interfaces account for this kind of behaviour?

Anything punted to the CPU at high rate could cause this kind of thing. 
That's why MLS limiters and CoPP are important on this platform, even 
with all their limitations.
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