Adjusting MTU of vmk10 or vmk11 results in Operation Failed
Article ID: 432220
Updated On:
Products
Issue/Introduction
- Administrators are unable to manually adjust the MTU of the NSX overlay vmkernel adapter (vmk10 or vmk11) directly from the vSphere Client UI on ESXi transport nodes:
Operation Failed!
The operation is not supported on the object.
It's not supported to update system owned vmknic vmk10 - Modifying the MTU value within the NSX Uplink Profile does not apply the intended change to the vmk10 interface.
Environment
VMware NSX
Cause
For transport nodes utilizing a vSphere Distributed Switch (VDS), the MTU of the vmkernel port is inherited from the VDS. Direct modification of the vmk10 MTU is restricted by design.
Additionally, the MTU setting configured within an NSX Uplink Profile (defaulting to 1700 bytes) strictly applies to transport nodes using an N-VDS (NSX Virtual Distributed Switch). This setting does not propagate to or override VDS-backed interfaces.
Resolution
To adjust the MTU of the vmk10/vmk11 overlay interface, the modification must be performed at the vSphere Distributed Switch (VDS) level.
Log in to the vSphere Client.
Navigate to the Networking inventory view.
Select the target vSphere Distributed Switch (VDS) providing the backing network for the NSX overlay traffic.
Navigate to Configure > Settings > Properties and click Edit.
Select Advanced and modify the MTU to the desired value (e.g., 1700).
Click OK to apply the changes.
The vmk10/vmk11 interfaces on the associated transport nodes will inherit the updated MTU from the VDS.
Additional Information
The minimum required Maximum Transmission Unit (MTU) is 1600 bytes. However, an MTU of 1700 bytes is recommended. This slightly higher value accounts for the potential expansion of the Geneve header, future-proofing the environment for various functions.
For optimal throughput and to improve performance for applications that generate large packets, the MTU should be increased to at least 9,000 bytes. For this change to be effective, the underlying physical infrastructure must support and be configured for a jumbo frame Maximum Transmission Unit (MTU) of 9000 bytes.
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