Multicast Query

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Aug 10th, 2010
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We have a single Vlan made up of a number of access switches and three 6509 switches. Predominantly the traffic is all Multicast and it is very high. When a multicast packet appears on the network, it is multicast to every port within the Vlan. The replying device then replies using Multicast but again the Multicast packet goes everywhere within that vlan.

Is there a way of getting the replying device only to send a return packet to the original source rather than everywhere ?

Thanks in advance ..

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Jon Marshall Tue, 08/10/2010 - 07:13
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IGMP snooping is your answer but you also need something to make the IGMP queries ie. IGMP snooping listens to responses to IGMP queries. Normally a L3 interface is enabled with PIM and that interface will make the IGMP queries but as you only have one vlan then you can use the "igmp snooping querier" function that is available on the 6500 switches.

So you need to enable IGMP snooping and the IGMP snooping querier function -


thstagman Tue, 08/10/2010 - 07:22
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Thanks Jon

I will pass this on to my collegue dealing with this issue.

With regards to the IP SLA a while back, which I did not get around to thanking you for (thanks). We chose in the end to bridge the offending router and that solved our wee problem.




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