NSX Edge status flaps between Up and Down after upgrade to NSX 4.2.1.0 or during upgrade pre-checks

Products

• VMware NSX

Issue/Introduction

The status of the NSX Edge in the NSX UI shows down intermittently, but when you click refresh at the bottom of the page, the Edges with status Down now show status Up, and other Edges show status Down. This continues ongoingly.

The issue started since the upgrade of NSX to version 4.2.1.0.

The NSX UI shows Edge status down as seen in the screenshot below:

 

Additionally, this issue can also be seen when upgrade pre-checks are performed prior to an NSX upgrade as seen in the screenshot below:

Environment

VMware NSX

Cause

This issue occurs due to incorrect DNS configuration on the NSX Edges such that the DNS servers aren't reachable from the NSX Edge or may have been decommissioned and may not exist.

Resolution

Check which DNS servers are configured on the NSX Edge, and if any of the configured DNS servers are unreachable from the Edge, they should be removed. 

The DNS configuration on NSX Edges can be configured via both CLI and API. For more information on how to do so, refer to the product documentation here: Configuring Appliances.