[f-nsp] High LP CPU After Upgrade 4001a to 54c Multicast

[Eldon Koyle]

We have seen issues when our MLXes receive multicast traffic for which
there have been no IGMP join messages sent (on edge ports).  I'm
assuming that not getting any PIM joins would have the same effect.
There are some applications that do not send IGMP messages if they
expect their traffic to remain on the same L2 domain.  Apparently if the
MLX doesn't have an entry for it, it punts it to the LP CPU.

To get an idea of which traffic is hitting the CPU, you can connect to
the LP (rconsole <slot_number>, then enable) and run 'debug packet
capture'.  That will show you a few packets as they hit the LP CPU, and
should at least tell you the source IP, interface, and multicast group
for the offending traffic.

HTH,

-- 
Eldon Koyle
-- 
BOFH excuse #319:
Your computer hasn't been returning all the bits it gets from the Internet.

On  Jun 03 10:32-0400, Walter Meyer wrote:
> We are seeing high CPU on our LPs after upgrading from 4001a to 54c on two
> MLXs.
> 
> We are using PIM-SM and the mcast process is using a large amount of LP
> CPU, but only after the upgrade. We are stable on the same config prior to
> the upgrade. Also, the MLX that is the RP for networks with a large number
> of multicast streams is the one that has a high CPU. The other core doesn't
> have an issue (aside from being unstable because of the other MLX with high
> CPU). We are pretty sure it has something to do with multicast routing we
> just can't figure out why.
> 
> We do have a large number of group/OIF entries spanning multiple physical
> ints and ves, but this shouldn't be an issue because of the OIF
> optimization feature on the platform...right? On 4001a and 54c we have a
> shareabilitiy coefficient / optimization of 98%...So it doesn't seem like a
> resource problem...But we can't figure out why the traffic is hitting CPU.
> 
> Has anyone seen mcast problems after upgrading or have any troubleshooting
> tips?

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