vSphere Distributed Switch (vDS) Multicast Filtering Mode: Reverting to Basic from IGMP/MLD Snooping

Products

• VMware vSphere ESXi 7.0
• VMware vSphere ESX 8.x

Issue/Introduction

When upgrading a vSphere Distributed Switch (vDS) to version 7.0 or 8.0, the Multicast Snooping mode is often enabled by default. While this is an efficiency feature designed to accurately direct multicast traffic, it can cause connectivity failures for legacy multicast applications or clusters that do not utilize IGMP membership reports.

Cause

The IGMP/MLD Snooping mode requires virtual machines to send IGMP join/membership reports so the vDS can populate its forwarding table. Applications like Microsoft NLB in multicast mode do not send these reports. Consequently, the vDS does not know which ports should receive the traffic and drops the multicast frames

Resolution

To restore connectivity, revert the Multicast Filtering Mode to Basic. In Basic mode, the vDS forwards multicast traffic to all ports within the same VLAN, similar to how a standard switch operates.

Configuration Steps

Review this command/process before running it.

1. Log in to the vSphere Client.
2. Navigate to the Networking inventory view.
3. Select the affected vSphere Distributed Switch.
4. Navigate to Configure > Settings > Properties.
5. Click Edit.
6. Select Advanced.
7. Locate Multicast filtering mode and change the selection from IGMP/MLD snooping to Basic from the drop-down menu.
8. Click OK to save the changes.

Additional Information

1. Multicast Filtering Modes
2. Understanding IP Multicast in ESXi
3. IGMP/MLD snooping when enabled makes Virtual IP in Microsoft NLB (Network Load Balancer) not reachable
4. Multicast Filtering Mode in vSphere 8.0: A Comprehensive Guide
5. Japanese KB:https://knowledge.broadcom.com/external/article/409434