Why the USG Flex H model display offline on the Nebula and how to resolve it?

Zyxel_Jeff

Question :

Users may encounter a situation where the USG Flex H model displays as offline on Nebula, as shown below:

This article will guide you on how to resolve it.

Answer :

The possible reason is a DNS resolution issue and the service port 4335 being blocked in the user's internet environment. This occurs because the USG Flex H series models use the domain name d2.nebula.zyxel.com to address the Nebula server with service port 4335.

So, users can utilize the nslookup tool either through the Web-GUI (path: Maintenance > Diagnostics > Network Tool NSLOOKUP IPv4) or via CLI (cmd diagnostics nslookup domain-name-or-ip domain-name d2.nebula.zyxel.com) to check if the USG Flex H model can resolve the domain name d2.nebula.zyxel.com normally or not, as shown below:

Also, please ensure that the USG Flex H model can successfully connect to Nebula via service port 4335. If it still has a problem, please contact the Zyxel support team for further assistance.