Tag Archives: vshield

IGMP versions requirement for VXLAN logical networks

Recently we were working on an issue were VXLAN Transport Multicast traffic was not being passed on the upstream physical switches causing an outage for the virtual machines that were hosted on these virtual wires.

Some Background on the environment:

This was a vCNS 5.5 environment with VXLAN deployed in Multicast mode. This was quite a big environment with multiple virtual wires deployed and multiple virtual machines connected to these virtual wires.
Virtual Machines were not able to communicate because multicast traffic was not being passed on the physical switches.

Upon further investigation it was revealed that IGMPv3 join’s were being received by the physical switch and since the physical switch had IGMPv2 enabled it pruned and ignored the IGMPv3 joins. So to resolve the issue, IGMPv3 was enabled on the upstream switches and the ESX hosts were able to join their multicast groups and the virtual machines were reachable on the network.

Starting with ESX 5.5, the default IGMP version on the ESX host has been changed to v3. This option is configurable and can be reverted to IGMPv2 using the ESX advanced settings,

Configuration–>Advanced Settings–>Net–>Net.TcpipIGMPDefaultVersion

Hope this helps someone that run’s into a similar issue.