NTP shows offline in VMware Cloud Director Availability 4.x

Products

• VMware Cloud Director

Issue/Introduction

• In the VMware Cloud Director Availability portal, the NTP status appears as offline for the replicator and tunnel appliances.
• Time synchronization shoes "NO" for "timedatectl" command.
• You may see error similar to the below:

Assuming task failed, as the status did not update in a timely fashion.

• Running a curl command against the NTP Server fails with the below error :

systemd-timesyncd[1488106]: Timed out waiting for reply from #.#.#.#:123
curl -kv #.#.#.#:123
* connect to #.#.#.# port 123 failed: Connection refused

Environment

VMware Cloud Director Availability 4.x

Cause

The issue occurs because UDP port 123, which is used for NTP communication, is blocked by the network firewall. This prevents the VCDA appliances (replicator and tunnel) from reaching the configured NTP server (#.#.#.# in this case).

Although the service (systemd-timesyncd) is running, it fails to receive a valid response from the NTP source due to this network-level restriction.

Resolution

• Engage the network team to confirm if UDP port 123 is allowed between the VCDA appliances and the configured NTP server.
• If not, allow UDP port 123 through the firewall to permit NTP traffic.
• After the port is allowed, verify the time synchronization status on the affected appliance using the timedatectl command:
   
  root@hostnamel [ ~ ]# timedatectl
               Local time: Mon 2025-07-21 03:05:44 UTC
           Universal time: Mon 2025-07-21 03:05:44 UTC
                 RTC time: Mon 2025-07-21 03:05:44
                Time zone: UTC (UTC, +0000)
System clock synchronized: yes
              NTP service: active
          RTC in local TZ: no
• Once the above output confirms that the system clock is synchronized and the NTP service is active, the issue is considered resolved.