Nexus 7710 VPC multicast duplication

[Vladimir Pysarenco]

Hi all,

We are faced into a trouble.

We have a pair of 7710 nexus, software 8.4.3 connected with VPC

And there is a lot of multicast in our network, only L2, without PIM.

IGMP querier is one of the switches.

After down\up of one of the links wee see that multicast traffic that was traversed through the peer link is duplicated (if source and destination are on the same switch - all is ok, if source on the sw1 and destination on the sw2 - multicast is duplicated). There are no any loops in the network.

What can be the reason of this issue?

Will "no ip igmp snooping mrouter vpc-peer-link" solve this problem? As soon as this command is global I am afraid doing it in production. 

Thanks!

[ss1]

I had the same issue on 3164Q used as a spine layer. It was duplicating the whole BUM traffic on my network topology and the reason was in the combination of VPC-enabled spine layer with both switches acting as an anycast-rp. 

Do you have any similar setup with you?

[Vladimir Pysarenco]

Hi,

As I said, we don't use PIM, only L2 multicast.

The issue was resolved after rebooting both switches. 

I think the reason was software upgrading with ISSU (software was upgraded the day before issue begins).

[ss1]

I'm glad to see the issue is resolved, however I never mentioned that I was having PIM-enabled vlans at the time this happened for me as well. 

By rebooting both switches you are swapping roles primary-backup which can otherwise be done by 'vpc role preempt'.