"MTU Mismatch Within Transport Zone" Alarm in NSX Manager UI for Security only.

Products

• VMware NSX

Issue/Introduction

NSX is configured for Security-only mode, the NSX Manager UI displayed  an alarm :

“MTU mismatch within transport zone. All switches must have the same MTU value. Click the uplink profile to update the values.”

Example - 

An MTU validation revealed that one of the  vSphere Distributed Switch (VDS) was configured with MTU 1600, while the remaining VDS switches and the Global Network Configuration were set to MTU 1500, leading to the mismatch alert.

Environment

VMware NSX

Cause

MTU values on all switches attached to the same Transport Zone not being consistent will cause connectivity issues.

Resolution

Steps yo resolve :-

1.  Update the MTU of the mismatched VDS to  match the value configured in the Global Network Configuration.
2.  Re-run the MTU check in NSX Manager to confirm consistency.
3.  Verify that the alarm clears successfully from the NSX Manager UI.
   
   

 

Additional Information

KB - MTU Mismatch Within Transport Zone Alarm in NSX Manager UI.

Docs - Guidance to Set Maximum Transmission Unit.