Configuring ESXi host with NSX-T Data Center, vCenter may generate alarm "Lost Network Connectivity"

Products

• VMware NSX Networking

Issue/Introduction

Symptoms:

• When you configure an ESXI host with NSX-T you may see an alarm in vCenter about ESXI disconnected. 
• The vmnic showing alarm is not related with the NSX-T configuration.
• In ESXi log /var/run/log/vobd.log the following messages maybe seen :

[vob.net.pg.uplink.transition.down] Uplink: vmnicX is down. Affected portgroup: Management Network. 1 uplinks up. Failed criteria: 128[vob.net.pg.uplink.transition.down] Uplink: vmnicX is down. Affected portgroup: vMotion. 0 uplinks up. Failed criteria: 128

• Note: vmnics above are not specific to NSX-T configuration.

Environment

VMware NSX-T Data Center

Cause

When the ESXI host is prepared for NSX-T, the datapath init script causes the device driver to preform a detach and re-attach operation on all the vmnics that use the same driver.

Resolution

This is a momentary event and will automatically recover.