logging IGMPv2 Joins and leaves

Unanswered Question
Oct 23rd, 2007


I have a couple of 3560/3750 switches and I am using IGMP snooping in a VLAN without an mrouter.

I am using IGMP Snoooping Querier in that particular vlan.

I need to get sure that MC traffic is forwarded at all times to some MC receivers.

Can I log if the switches adds/removes dynamic IGMP snooping entries?

Are there some useful SNMP traps?


I have this problem too.
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owillins Mon, 10/29/2007 - 06:43

following commands are used for SNMP notification for multicast traffic.

snmp-server host {hostname | ip-address} [traps | informs] [version {1 | 2c | 3 [auth | noauth | priv]}] community-string [udp-port port] [notification-type]

snmp-server enable traps ipmulticast

ip multicast heartbeat group-address minimum-number window-size interval

for more info:


ROBERT SAURER Mon, 10/29/2007 - 07:16

Oscar, thanks for your reply,

but 12.4T is not an option because I have Catalyst 3560/3750 switches with a 12.2SE train. (a pure L2 switching environment with no IPv4 MC routing; all senders and receivers are in the same subnet)

I do not need to monitor if a router receives packets for a particular MC group in a particular time window.

I would like to check for how long a particular l2 port has joined a MC group (without disruption).

As far as I understand my IGMP Snooping querier sends a general IGMP query every 60s with a max response time of 10s to all hosts in the subnet.

Every receiver starts a random timer between 0 and max response time. One receiver will answer first and the reply will be seen by the MC router (I don't have one) and by all other receivers.

In case of a IGMP snooping environment I suppose that the switch replicates the general query to each host, but will not send replies back to other receivers. So I suppose each receiver has to reply.

I'm not sure if the switch removes the port from the mc group if it doesn't see a reply within 10s or if it doesn't see a reply for 3 times the query interval.


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