Intra-VLAN multicast traffic Nexus 7000

Unanswered Question
Aug 25th, 2011

Hi everybody,

I have 2 couples of Nexus 5548 connected to 2 Nexus 7010 core switches as you can see on attached network layout.
Multicast source and multicast receiver are assigned to the same VLAN. This VLAN is only Layer 2 on Nexus 7010.

If I connect multicast source and receiver on two different ports on the same FEX, the receiver is able to join multicast group and get multicast traffic.

If I connect the source on FEX 111 and the receiver on FEX 121, the receiver cannot get multicast traffic. The only way to have the receiver getting multicast traffic is to configure SVI on Nexus 7010 and activate PIM on it.

Why I need to configure PIM if source and receiver are in the same VLAN?
How can I avoid this Layer 3 configuration on Nexus 7010?


I have this problem too.
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Jerry Ye Thu, 08/25/2011 - 18:41

Jon's link explains the problem in your topology.

The multicast receiver on the other FEX has no knowledge of the source (over the trunk) because of igmp snooping is enabled.

To resove this problem, you have 2 solution, which you already know about the first one - to configure SVI and enable PIM.

The second solution is to enable igmp snooping querier. In Nexus, the configuration is under vlan xx. Here is an example:

vlan 99

ip igmp snooping querier x.x.x.x

x.x.x.x is an ip address not used by any host. I am assuming this is an L2 only network, you can use any reserved IP, such as x.x.x.1 or x.x.x.254.



s-durando Thu, 08/25/2011 - 22:02


I have to configure ip igmp snooping querier on both Nexus 7010 and 5548, is it true?



Jon Marshall Fri, 08/26/2011 - 04:14

You only need one switch to be an IGMP querier but you need all switches to be running IGMP snooping.



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