Multicast dropped and invalid packets

[david.bradley]

Hi,

I've read all I can on the cisco.com site and not found a good explanation of dropped and invalid IGMP packets.

This output is displayed from a cat os 'show igmp statistics', dropped packets and also invalid packets.

What are these and what can cause them??

Thanks

[Georg Pauwen]

Hello David,

do you happen to see entries in your logs such as:

%MCAST-6-IGMP_PKT_DROPPED: IGMP: IGMP Queue full (high packet rate/CPU busy), dropped [dec] packet(s) in last 5 minutes

According to CCO, ´this message indicates that the IGMP packet queue is not able to accommodate additional packets. Any additional packets will be dropped without processing.

Recommended Action: Reduce the IGMP packet rate to prevent packets from being dropped´

You might want to try and enable IGMP Snooping (set igmp enable) on your switch, in order to reduce the number of IGMP packets sent...

Regards,

GP

[david.bradley]

Thanks,

Yes I've seen that syslog entry, so that explains the drops. I'm still not sure about the invalid packets, perhaps this is also a symptom too.

I think IGMP snoop is enabled but I will check.

Dave