[c-nsp] Nexus Layer 2 Multicast and IGMP querier

[Stoward, Matt]

We are in the middle of a large (1000s) of physical server (on IOS switches) to virtual server (on NX-OS) migration and more and more we are stumbling on weird situations like servers having back-to-back connections for heart beats where we have to make a non routable VLAN and run them out to all the prospective hosts to emulate this connectivity.

Some applications need L2 multicast to work and because we don't have an any SVIs in these non routable VLANs we have been configuring up an IGMP querier under the VLAN configuration mode to get this to work but we are becoming reluctant to keep on creating more and more and more VLANs.

I'm hoping to be able to run a general purpose clustering VLAN for this situation but I think I have a problem where one cluster might want to talk on say 192.168.34.0/24 and another on 10.10.10.0/24 and as the VLAN only allows one igmp querier address multicast will break for servers that talk on another range that the querier address does not belong to (e.g. igmp snooping querier 192.168.34.254 means that 192.168.34.0/24 cluster will work but a cluster talking on 10.10.10.0/24 will not work).

We run a bunch of N2Ks so there is some unwillingness to turn off the multicast flood protection that would turn multicast into broadcast due to the 2K uplink cost of having lots broadcast on the network.

I'm struggling to find documentation that confirms whether I can get different IP range IGMP working on NX-OS, and I'm hoping someone can confirm expected behaviour. I suspect I'm stuffed, and will need to either run some VLANs that turn off the multicast flood protection or commission even more VLANs.

Regards,
Matt