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IGMP snooping not working on Cat6509 after a network shutdown.

Because of a building maintenance activity, we had to completely shutdown our network for a couple of hours.

After reboot, multicast traffic sometimes stops flowing from application servers to remote clients.

Remote clients are connected to 2 Ascend TNT routers (one primary, one backup) that are collapsed on

a Catalyst 6509 to which also servers are connected. Only the primary TNT router doesn't receive multicast and the 2nd is working perfectly. Usually after resetting the primary TNT, multicast starts flowing again (i.e. 6509's TNT port is registered in the multicast group) for 3 to 6 hours or until applications are shut in the evening. But next day problem shows again.

Disabling IGMP snooping ("set IGMP disable") on Catalyst 6509 solves the problem.

We don't have layer 3 multicast enabled. Multicast applications have been working correctly with the Catalyst and TNT's for the last 8 months and both Catalyst, TNT's and servers have been separately shut down several times.

I know that the problem could be on the TNT, but it's been there for almost 3 years without any problem...

I've looked in the BUG repository without luck...

any hint?

WS-C6509 Software, Version NmpSW: 7.5(1)



Re: IGMP snooping not working on Cat6509 after a network shutdow

It could be possible that after the shutdown, the icmp joins are sent out on the wrong interfaces.

chek and correct it if this is the issue.

Community Member

Re: IGMP snooping not working on Cat6509 after a network shutdow

Not sure....

FastEthernet of Ascend TNT has igmp forwarding "yes".

However no membership report are sent out after a Catalyst 6509 "host membershp query" (the backup TNT replies correctly to it). I have little control (and experience) on the Ascend box and most of my checks are done by sniffing Catalyst's ports.

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