ERROR: “<IP Address> failed. Validating NTP servers is sometimes unreliable. You may need to retry."

Products

• VCF Operations/Automation (formerly VMware Aria Suite)

Issue/Introduction

1. Time synchronization on VMware Aria Operations for Logs fails when connecting to the configured NTP servers, displaying the error: “<IP Address> failed. Validating NTP servers is sometimes unreliable. You may need to retry.”
2. Migrating all Aria Operations for logs nodes to particular host with ESXi host to be the NTP server then set up affinity rules with VM/Host groups so that the Aria Operations for Logs VMs stay on the particular host to address latency issues.  Now want to now configure a new NTP server in Aria Operations for Logs. 
   
   1. Testing the connectivity between Aria Operations for Logs and the ESXi host set as NTP server fails.
   2. Running the cURL command to check the connectivity fails.

      curl -v telnet://<IP Address>:<Port Number>

   3. The /storage/core/loginsight/var/runtime.log shows errors similar to below when testing the connection for the new NTP configuration

      ["CheckPerformer-thread-1"/<IP Address> WARN] [com.vmware.loginsight.prodcheck.lib.NTPSyncCheck] [
      Time synchronization cannot be confirmed.
      Check availability and health of the NTP servers.

Environment

VMware Aria Operations for Logs 8.18.x

Cause

NTP traffic on port 123 is being blocked by firewall rules, causing time synchronization failures in Aria Operations for Logs.

Resolution

1. Confirm that no antivirus software is blocking communication with the NTP server.
2. Reorganize the cluster and created affinity rules to exclude the affected ESXi host, in accordance with the documentation Create a VM-Host Affinity Rule.