Multicast working like broadcast

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Jun 24th, 2007
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I am running a multicast application on my 3750 switch which has only 1 vlan configured. I have not done any specific configuation and i suppose igmp snooping is enabled by default. Multicast works but all users in the vlan receive multicast packets even if they have not requested for it. What could be issue...

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mohammedmahmoud Sun, 06/24/2007 - 03:51
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It seems like an igmp snooping problem, can you please elaborate on your network topology.


Mohammed Mahmoud.

zubairjalal Sun, 06/24/2007 - 04:15
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I have a Cisco 3750 switch with multiple Vlans configured. My source and receivers are sitting on this switch only and both are in VLAN 56. I am running a multicast stream at My receivers recieve the traffic but my other users in VLAN 56 also receive the traffic..this results in high latency for other application and users in vlan 56.

Jon Marshall Sun, 06/24/2007 - 06:47
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You need to have an IGMP querier so that the IGMP snooping can listen to the replies ie. igmp snooping is listening to answers but someone must ask the question. Usually this is done by a router interface but on the 3750 you can use the "igmp querier" funtionality which will achieve the same thing.

Attached is a link to configuring the IGMP querier on a 3750




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