Virtual machines cannot communicate using IPv6 multicast groups on same DVport on DVS 7.0 and higher

Products

• VMware vSphere ESXi

Issue/Introduction

Running ONTAP (NetApp Operating System) VM on a vDS/DVS with multicast filtering (IGMP/MLD snooping MLDv2).

Symptoms:

For redundancy at least two ONTAP virtual machines (VMs) are deployed on different ESXi hosts. The ONTAP VMs support only IPv6 for communication amongst each other.
VMs running ONTAP will not be reachable on their IPv6 addresses, when IGMP/MLD snooping is enabled on the vDS/DvS (Distributed virtual Switch) 7.0 and higher.

Environment

VMware vSphere ESXi 7.x
VMware vSphere 7.0.x

Cause

The MLD snooping table needs to be build up with MLD join messages.
The MLD join message (reply) is not sent by the ONTAP VM and the DVS/vDS cannot build the lookup table. Therefore, the ONTAP VM can never join the multicast group, hence, the subsequent packets will be dropped.

Resolution

ONTAP VM is not supported when IGMP/MLD snooping is enabled on VDS multicast filtering mode. This is under review by NetApp. Please contact your partner/provider for more information.

Workaround:
Set multicast filtering mode (on vDs) to "Basic" (= Legacy filtering).
On vDS/DVS 7.0 and higher this is set to "IGMP/MLD snooping" by default.

Additional Information

https://kb.vmware.com/s/article/75217 - IGMP/MLD snooping when enabled makes Virtual IP in Microsoft NLB (Network Load Balancer) not reachable (75217)

Impact/Risks:
No communication between ONTAP VMs, or communication between the physical NetApp filers and the ONTAP VMs (unless the ONTAP VMs establish the connection to the filers first).