NSX Alert: Host added to more than one vxlan prepared NSX Distributed Switch. Host should be part of only one NSX configured distributed switch

Products

• VMware NSX

Issue/Introduction

Symptoms:
The ESXi host displays an alert: "NSX Alert: Host added to more than one vxlan prepared NSX distributed switch. Host should be part of only one NSX configured distributed switch"

Environment

VMware NSX for vSphere 6.4.x

Cause

This alert was introduced in NSX 6.4.2 and can be misleading. It is displayed when a host that is prepared for NSX is added to any vDS, regardless of whether the new vDS is prepared for VXLAN or not.

If indeed the ESXi host is added to two distributed switches both of which are used by NSX for VXLAN, this may result in a datapath outage. The DLR functionality can break down because the host will have two VDR ports.

Resolution

Check if the host is added to two VXLAN prepared switches. 

• If it is not, you can safely ignore the alert.
• If it is, disconnect the host from the switch that was not used in Host Preparation. 

Starting NSX 6.4.5, the wording of the alert has been updated so that it is no longer misleading:
"NSX Alert: Host is added to more than one DVS. Please ensure that host is NOT added to multiple DVS prepared for vxlan using NSX."