MTU Mismatch Within Transport Zone Alarm in NSX Manager UI.

Products

• VMware NSX

Issue/Introduction

Event ID: mtu_check.mtu_mismatch_within_transport_zone

Alarm Description

• Purpose: Check if there is MTU configuration mismatch between Transport Nodes (ESXi, KVM and Edge) attached to the same Transport Zone.
• Impact: MTU values on all switches attached to the same Transport Zone not being consistent will cause connectivity issues.

Environment

VMware NSX 
VMware NSX-T Data Center

Resolution

Steps to Resolve:

1. For 3.2.0 and higher
   
   Recommendation:
   
    Navigate to System | Fabric | Settings | MTU Configuration Check | Inconsistent on the NSX UI to check more mismatch details.
2. Retrieve the MTU details on the transport zone using the GET API call  "https://<nsx-mngr-ip>/api/v1/global-configs/SwitchingGlobalConfig"
   
   Test screenshot:
   
3. Set the same MTU value on all switches attached to the same Transport Zone by invoking the NSX API "PUT /api/v1/host-switch-profiles/" with mtu in the request body, or API "PUT /api/v1/global-configs/SwitchingGlobalConfig" with "physical_uplink_mtu" in request body.
   
   

 

The same can also be fixed by navigating the System >> Fabric >> Profiles >> Uplink Profiles, and setting the MTU value in the uplink profiles to the value set for VDS.