MTU Validation error on ESXi host after upgrade or when configuring NSX

Products

VMware NSX

Issue/Introduction

This issue is observed in two different ways as follows:

1. After performing an upgrade of NSX to version 4.2.3:

Immediately after an upgrade of NSX to version 4.2.3, the following error is observed on all upgraded ESXi hosts under the System -> Fabric -> Hosts tab of the NSX UI: 9531: VDS [<name>] does not need field MTU to be specified in its uplink profile [BaseHostSwitchProfile/<UUID>]. Keep the field MTU in uplink profile for a VDS switch empty. Field MTU for VDS has to updated from vSphere. (Error code: 9531)
SDDC Manager is in use and this uplink profile was SDDC created
Screenshot of this tab:

2. While configuring NSX on a cluster as follows:

When attempting to configure a host as a transport node, it fails with:
Error: VDS [<name>] does not need field MTU to be specified in its uplink profile [BaseHostSwitchProfile/<UUID>]. Keep the field MTU in uplink profile for a VDS switch empty. Field MTU for VDS has to updated from vSphere. (Error code: 9531)
Review of Uplink Profiles in use shows MTU setting other than "1700 (Global MTU)", the default value displayed when the profile's MTU field is left blank. The example below from a generic lab environment shows an uplink profile with an MTU configured to a custom value.

Environment

VMware Cloud Foundation 5.2.2
VMware NSX 4.2.3

Cause

Prechecks when attempting to add a node to a cluster will fail if an uplink profile has an MTU setting that is not consistent with the Virtual Distributed Switch the host will connect to.

Refer to Configuring a vSphere Distributed Switch which states: "As a host transport node that is prepared using VDS as the host switch, the MTU value needs to be set on the VDS switch in vCenter Server."
Users can still use Uplink Profiles to set MTUs if the settings are not being applied to a Virtual Distributed Switch.

Resolution

This issue is resolved in VMware NSX 4.2.4 or later, available at Broadcom downloads.
This release adds an upgrade precheck that alerts the administrator to this condition before the upgrade proceeds.

If you are having difficulty finding and downloading software, please review the Download Broadcom products and software KB

WORKAROUND:

At System > Configuration > Fabric > Profiles, select and edit the applicable Uplink Profile.
Delete the MTU value at the bottom of the window to leave it blank, then click Save.
Once the uplink profile does not list a MTU value anymore, you can run the normal process for Preparing ESXi Hosts as Transport Nodes and it should no longer fail the precheck.

*Note, if editing the profile is not permitted over being in use by Transport Nodes, this results in an error such as:

The uplink host switch profile is referenced by 4 Transport Node(s). The MTU for VDC switches should not be specified in NSX. Please update the MTU in vCenter. (Error code:8548)

Work around this limitation by duplicating the existing uplink profile into a copy. Unset the MTU value in this copy, and either assign the copy profile manually (via the action Configure for NSX) to the Transport Node hosts or into the Cluster's Transport Node Profile directly if the cluster binds a TPN. This will all edits to the original uplink profile in case it needs to be re-applied, like if it was provisioned from an external solution managing the cluster, such as VCF. Once the MTU value is unset you can reassign this corrected, original uplink profile back onto the hosts and delete the copy profile.

How to update Uplink Profile under Transport Node Profile :
System > Configuration > Fabric >> Hosts >> Transport Node Profile >> Edit Host Switch >> Uplink Profile [ Choose the new Uplink Profile created without MTU value set]
Click ADD >> then APPLY.

Additional Information

VMware NSX 4.2.4 Release Notes

Create an Uplink Profile explains all the various settings in an uplink profile that can be applied to a Transport Node by selecting as part of a Transport Node Profile attached to a host or a cluster of hosts configured as transport nodes in NSX Manager.
Also see Guidance to Set Maximum Transmission Unit with other helpful information.

If you are contacting Broadcom support about this issue, please provide the following:

vCenter Server and ESXi host log bundles for the affected cluster
Ensure log date range covers the full date of the event(s) being investigated. When in doubt, retrieve logs for all time.
NSX Manager log bundles
Text of any error messages seen in NSX GUI or command lines pertinent to the investigation

Handling Log Bundles for offline review with Broadcom support