VM experiences packet loss after upgrading Distributed Virtual Switch (DVS) from version 6.5 to 7.x

Products

• VMware vSphere ESXi

Issue/Introduction

After upgrading the Distributed Virtual Switch (DVS) from version 6.5 to 7.x, virtual machines experience intermittent network packet loss.

Environment

VMware vSphere ESXi

Cause

• In DVS version 6.x, the default multicast filtering mode is set to Basic. However, after upgrading to version 7.0, the default changes to IGMP/MLD Snooping. Refer: Multicast Filtering Modes
• IGMP/MLD snooping monitors the multicast group memberships between virtual machines by analysing IGMP (for IPv4) and MLD (for IPv6) messages generated between the same.
• When IGMP/MLD snooping is enabled on the DVS, by design multicast traffic is been forwarded.
• When multicast traffic is received by upstream switches/routers having Cisco Layer 2 port security check enabled, ports may be blocked due to port security violations.

Resolution

Change the multicast filtering mode on the DVS from IGMP/MLD Snooping to Basic.

Steps:

1. Select the distributed switch in the networking tab on the VCenter.
2. Right click on the DVS, edit settings.
3. Click on the Advanced tab and change the multicast filtering mode.

In case you want the IGMP/MLD snooping enabled on the DVS, you can disable the Cisco Layer 2 Port security check at the upstream switch/router to avoid blocking of the ports due to expected multicast traffic post upgrade.

Additional Information

Multicast Filtering Modes