[c-nsp] Cat4500 High CPU with Multicast Stream

[Alexander Clouter]

Antonio Soares <amsoares at netcabo.pt> wrote:
> 
> I have a customer with a few 3560/3750's and one 4500/SUP5 acting as the
> core switch.
> 
> For some reason, when a user start one multicast stream, the 4500 suffers
> high cpu utilization and the network is affected. Only the 4500 suffers of
> this problem, the 3560/3750's don't have any complaints.
> 
> I see that the 4500 is a CEF based platform and I know that IP Multicast is
> not supported in the CEF path. So I was expecting to have this traffic
> switched in hardware or fast-switched. But a packet capture shows me that
> the traffic goes to the cpu. I used this debug and output to confirm this:
> 
> debug platform packet all receive buffer
> 
> show platform cpu packet buffered
> 
> The processes that eat most of the cpu are "Cat4k Mgmt LoPri" and "Cat4k
> Mgmt HiPri". We thought this could be a bug and we upgraded the 4500 to the
> latest release but the problem is exactly the same. The multicast stream is
> processed by the cpu.
> 
> Anyone has seen this before ? Is this normal behavior of the 4500 ?
> 
> Usually the multicast streams are destined to 224.x.x.x. The end users do
> not respect the 239 rule.
> 
> 
Sounds like the following might help:

http://www.gossamer-threads.com/lists/cisco/nsp/128799?do=post_view_threaded

It's the following lines you might need:
----
mls rate-limit multicast ipv4 non-rpf 100 10
mls rate-limit multicast ipv4 partial 250 100
----

Or something similar to them.

Cheers

-- 
Alexander Clouter
.sigmonster says: I'm not tense, just terribly, terribly alert!