Symptom

In certain conditions, multicast packets that are to be punted may be punted on both the ingress and egress. This does not cause any direct functional problems. The problem is the wasted bandwidth on the punt path, and deceiving counters. The additional punt path traffic could cause rate limiting that would otherwise not occur. The punt counts can be seen in the "SW Forwarding Counts" of the "sh mfib route detail" command.

Conditions

This condition can occur when using the "join-group" parameter to IGMP join a multicast group as shown. router igmp interface GigabitEthernet0/0/0/38 join-group 225.0.0.0 ! ! Packets can then be punted on the "A" (ingress) interface, and the "F/EG" (egress) interface.

Workaround

There is no workaround using the "join-group" configuration. Note that "static-group" configuration, or having the groups joined via IGMP joins will not cause the problem. Recovery: No recovery is necessary.

Further Problem Description