While adding a vmnic to the Distributed Virtual Switch (DVS), the operation fails with the following error message: "Unable to add uplink! The MTU used by this DVSwitch is not supported by the NIC being added.”

Products

• VMware NSX

Issue/Introduction

• While adding a vmnic to the Distributed Virtual Switch (DVS), the operation fails with the following error message:
  “An error occurred during host configuration: Operation failed, diagnostics report: Unable to add uplink! The MTU used by this DVSwitch is not supported by the NIC being added."
• It was confirmed that the MTU configured on the DVS is set to a value higher than 9000.
• Error message as follows:  

Environment

vCenter 7.x, 8.x

Cause

The MTU on the DVS is incorrectly configured with a value greater than 9000.

Resolution

• ESX/ESXi supports a maximum MTU size of 9000. Any value configured beyond this limit is not supported and results in failure when adding physical uplinks to the DVS.
• Reduce the MTU value on the DVS to 9000.
• Note: This change should be performed during a scheduled maintenance window, as DVS configuration changes apply to all hosts associated with the switch.