[c-nsp] Cat4500 High CPU with Multicast Stream

[Antonio Soares]

The TTL=1, they use VLC and this is the default TTL value.

We found in the meanwhile that if the stream is sent to 239.x.x.x, there is
no impact on the 4500's cpu.

If the stream destination is somewhere in the 224.x.x.x range, the cpu goes
to the maximum. The packets are processed by the cpu.

I understand the 4500 is listening to the 224.0.0.0/24 address space, so
this must the reason we have this behavior.

We don't have IP Multicast enabled. I'm thinking about enabling IP Multicast
and only accept the 239 range.

Any comments ?


Regards,

Antonio Soares, CCIE #18473 (R&S/SP)
amsoares at netcabo.pt
http://www.ccie18473.net



-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Antonio Soares
Sent: quarta-feira, 13 de Julho de 2011 13:26
To: 'Chris Evans'
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] Cat4500 High CPU with Multicast Stream

I will check that, in fact the 4500 is the first hop router.

 

 

Thanks.

 

Regards,

 

Antonio Soares, CCIE #18473 (R&S/SP)
 <mailto:amsoares at netcabo.pt> amsoares at netcabo.pt

 <http://www.ccie18473.net> http://www.ccie18473.net

 

 

From: Chris Evans [mailto:chrisccnpspam2 at gmail.com] 
Sent: quarta-feira, 13 de Julho de 2011 13:12
To: Antonio Soares
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] Cat4500 High CPU with Multicast Stream

 

Check the ttl on the multicast stream. A ttl of 1 will cause it to hit the
CPU of your first hop router.   

On Jul 13, 2011 8:02 AM, "Antonio Soares" <amsoares at netcabo.pt> wrote:
> Hello group,
> 
> 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.
> 
> 
> Thanks.
> 
> Regards,
> 
> Antonio Soares, CCIE #18473 (R&S/SP)
> amsoares at netcabo.pt
> http://www.ccie18473.net
> 
> 
> 
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