Multicast traffic between VLAN and Overlay segment through edge bridge doesn't work

Products

• VMware NSX

Issue/Introduction

• Multicast traffic connectivity issue in an environment using Edge bridging
• Multicast traffic from VLAN does not reach VMs on overlay segments
• IGMP reports from overlay VMs is not seen on the VLAN side
• When VMs from VLAN and overlay are on the same host, multicast works
• When the receiver is moved to different host then that of the multicast router / switch, the multicast joins are not forwarded to the router. 

Environment

VMware NSX 3.2.x, 4.1.x, 4.2.x

Cause

The virtual switch drops the Internet Group Management Protocol (IGMP) reports that come from overlay VM ports to host uplinks. The physical multicast router/switch never learns of the VM's interest to join the multicast group.

Resolution

NSX-T 3.1.2 introduced a switch option which allows IGMP/MLD packets from VMs to be forwarded onto Uplinks. This is disabled by default.
This must be enabled on all ESXi hosts where the overlay VMs participating in bridging are located.

From vCenter UI

1. In the Inventory view, ESX host > Configure > System > Advanced System Settings > click Edit
2. Update Net.SendIGMPReportToUplink setting to a value of 1

or

Directly on an ESXi host:

  esxcli system settings advanced set -o "/Net/SendIGMPReportToUplink" --int-value 1