Unable to change or set MTU value of vmkernel (vmk)bound to iSCSI adapter from vCenter GUI.

Products

• VMware vSphere ESX 8.x
• VMware vCenter Server 8.0

Issue/Introduction

Before binding the iSCSI adapter to the vmkernel, MTU changes on the vmkernel can be made. When trying to change the MTU value, or any other value from the vCenter GUI on an iSCSI adapter bound to a vmkernel, you are unable to do so. 

Once changes are made, the settings will revert back to their original values, where no updates or error codes are shown. 

Also, when trying to change the MTUs in a storage VMK, it will give an warning below and revert the change. 

Environment

VMware vCenter Server Version: 8.x

VMware vSphere ESXi 8.x

Cause

A reconfiguration process is not triggered if the user makes a change for a vmkernel (vmk) that is connected to an iSCSI adapter. 

Resolution

Workaround: 

Change the MTU value from the ESXi host cli using the below command: 

• esxcli network ip interface set -m=<MTU Size> --interface-name=vmkX

Or perform this change from the ESXi host UI: 

Additionally, the change can be made from the vCenter itself:

1. Navigate to the host.
2. Click the Configure tab.
3. Under Storage, click Storage Adapters, and select the appropriate iSCSI adapter from the list.
4. Click the Network Port Binding tab
5. Select the Port Group
6. Click the Remove icon.

Resolution is targeted for the next release 9.x of VMware vCenter Server and VMware vSphere ESXi.