Network Switch [Connectivity] - Troubleshoot NTP issues (Nebula / Standalone)

Zyxel_Tina

Zyxel switch uses NTP protocol to automatically synchronize system date and time with global servers. This makes sure users could find the logs with correct time in the event log. But once the synchronization fails or incorrect, it could cause network issues. This topic will guide you how to troubleshoot the NTP synchronize failed with some quick check and test for your devices.

 

Troubleshoot steps

 

1.1 Does the switch connect to the Internet?

1. Access to your switch via Telnet/SSH/console.
2. Ping 8.8.8.8 and default gateway.
   
3. If ping 8.8.8.8 fail and ping default gateway fail. Please check the routing and physical connection between switch and gateway.
4. If ping 8.8.8.8 fail and ping default gateway OK. Please check your default gateway for the Internet connection.

 

1.2 Can the switch resolve NTP server’s domain name that device used?

1. Access to your switch via Telnet/SSH/console.
2. Ping *.pool.ntp.org. Note * can be 0, 1, 2, 3.
3. Please check if the NTP server’s domain name that device used can be resolved.
   Note: the IP address of NTP server is dynamic.
   
4. If the switch shows “unknown host”, please check your DNS server setting or try 8.8.8.8 as DNS server on Switch (You may configure it on Local GUI of Switch).
   

1.3 Are there any firewall rule blocks NTP protocol?

1. Please check if your network has blocked 123 port.
2. Access to your switch via Telnet/SSH/console.
3. Use command “show time” to check if the NTP synchronize correctly or not.

Note: the Nebula devices will trigger the synchronization again after 30 seconds once it synchronizes failed.