After changing MTU size on vDS, the host still shows the vDS at the previous MTU size via CLI

Products

• VMware vSphere ESXi

Issue/Introduction

After changing MTU size on a vSphere Distributed Switch (vDS), the host still shows the vDS at the previous MTU size via CLI.

Specifically, the below command showing the switches on the host shows the vDS in question with an incorrect MTU:

esxcfg-vswitch -l

Additionally, the below command will show the MTU of the physical NICs that are on the vDS incorrectly as well:

esxcli network nic list

This issue may be seen after changing the MTU on the ESXi hosts' vmkernel adapters as well, however the incorrect MTU presentation is limited to the vDS itself.

Cause

The vDS is managed at the vCenter level, but every host retains a "proxy copy" of the vDS. When changes are made to the vDS itself, these configurations are updated on the hosts' local proxy copy of the vDS.

In certain circumstances though, such as if the host is not reliably connected to the vCenter due to an MTU mismatch concerning the management network, the change may not be pushed to the hosts correctly.

Resolution

Remove the host from the vDS by migrating all networking to a different vDS or standard switch temporarily, then detach the host from the vDS to remove the proxy copy.

Once complete, the host can be migrated back to the vDS (once any underlying host connectivity issues have been resolved), and a new proxy copy will be deployed on the host with the correct configurations.

See Remove Hosts from a vSphere Distributed Switch for more information about the detachment process.