VM network connectivity issues after NSX upgrade due to mac learning being disabled

Products

• VMware NSX

Issue/Introduction

The environment has been upgraded from NSX 3.2.x to 4.2.x.

• VMs are unable to communicate with each other.
• Missing learned MAC addresses on port interfaces

Below logs will be noticed:

grep "com.vmware.vswitch.port.macManagement" commands/dump-vswitch-info-nsx.py.txt
com.vmware.vswitch.port.macManagement = mac change allow; learning disabled; flooding disabled; macLimit 4096; macLimitPolicy: allow

Environment

VMware NSX 

Cause

• NSX Impactor (3.2.x) may expect MAC learning to be enabled on the default MAC discovery profile (default-mac-discovery-profile).
• Post upgrading to NSX 4.1.x or 4.2.x, MAC learning is disabled on the default profile, which can lead to datapath issues.

Resolution

This is an expected behavior in NSX 4.1 as default MAC discovery profile has mac learning disabled.

Workaround :

Environments using NSX Keeper (4.1.x) or Longview (4.2.x) can use a custom MAC discovery profile with MAC learning enabled instead of the default default-mac-discovery-profile.