Skyline Health findings shows "vMotion network configuration finding for vSphere Distributed Switch"

Products

• VMware vCenter Server
• VMware vSphere ESX 8.x
• VMware vSphere ESX 7.x

Issue/Introduction

• vMotion network configuration finding for vSphere Distributed Switch is listed in Skyline Health findings.

• Expanding this finding shows the following information:

  • A mismatch between the MTU settings of a vMotion vmkernel adapter and a vMotion Ditributed Switch connected to it might lead to a failure in vMotion operations. Both MTU settings must match so that vMotion Operations can execute successfully. Click the Ask VMware link above for more details and a resolution.

• To view the list of hosts which are impacted, click on the Troubleshoot button under this finding.

Environment

VMware vCenter Server

VMware vSphere ESX

Cause

Skyline Health will report an MTU mismatch when the configured MTU of a vMotion VMkernel adapter differs from that of its connected vSphere Distributed Switch (VDS).

Resolution

There are two scenarios where this finding can be reported:

• SCENARIO 1:
  • MTU configured on vMotion VMkernel adapter : 1500
  • MTU configured on Virtual Distributed Switch : 9000 (or any value greater than 1500)

In this situation, change the MTU on the vMotion VMkernel adapter to 9000. Ensure that Physical Switchports connected to the Physical Network adapters [vmnicX] attached to this VDS can support 9000 MTU.

 

• SCENARIO 2:
  • MTU configured on vMotion VMkernel adapter : 9000 (or any value greater than 1500)
  • MTU configured on Virtual Distributed Switch : 1500

In this situation, change the MTU on vMotion VMkernel adapter to 1500.

 

Initiate a RETEST of Skyline Health by Clicking on vCenter Server -> Monitor -> Skyline Health -> RETEST.

Additional Information

If the MTU on the vSphere Distributed Switch has to be changed, please refer to Enabling Jumbo Frames on virtual switches

To change the MTU on a VMkernel adapter, following steps can be performed:

*NOTE: Ensure that no vMotion operation is in progress before changing the MTU. 

•  Option 1. Change via GUI:

1. Open vSphere Client.
2. Select the affected host in the navigation pane.
3. Navigate to the Configure tab.
4. Under Networking, click on VMkernel Adapters.
5. Click on Vertical Ellipsis '⋮' for the vMotion VMkernel adapter and click on Edit.
6. Change the MTU value and click OK.

•  Option 2. Change via CLI:

1. Open a SSH session to the affected ESX host.
2. Run the following command to change the MTU on VMkernel adapter:

esxcli network ip interface set --mtu=<mtu_value> --interface-name=vmk<#>