Linked vCenters (ELM) cannot see each other and are missing from vCenter UI

Products

• VMware vCenter Server

Issue/Introduction

Multiple vCenter servers are joined in enhanced linked mode (ELM) but not all vCenter servers are visible in the UI for some vCenter servers.
Curl attempts against ports 443, 389, 2012, 2020 between impacted vCenter servers inconsistently succeeds and fails.

Environment

vCenter 7.x
vCenter 8.x

Cause

Unstable network connectivity between the vCenter servers. 

Resolution

• Engage networking team to investigate the network path and routing between vCenter servers.

Additional Information

Using Curl to test port connectivity in VMware vCenter Server Appliance