VM vMotion creates packet loop Issues when using NSX Service Insertion and a vDS configured for IGMP/MLD snooping

Products

• VMware NSX
• VMware NSX-T Data Center

Issue/Introduction

In the presence of NSX Service Insertion, and a vDS with multiple uplinks and IGMP/MLD snooping enabled, multicast packets (including SSDP) may get looped back from one uplink to another causing a multicast storm.

Cause

This is a known issue affecting NSX versions below 4.2.

When IGMP/MLD snooping is enabled (which is the default on vDS 7.0+), after vMotion of VMs using SSDP, the host switch may loop the SSDP packets with MAC address of VMs running on other hosts that are not involved in vMotion. The vSwitch then forwards incoming SSDP packets back out to the external network/switches.

 

Resolution

This issue is resolved in NSX 4.2 - Release Notes (Issue 3347327)

Workaround:

Change multicast filter mode from IGMP/MLD snooping to Basic (legacy), or block SSDP packets (port 1900).