Why Does DDNS Fail on USG FLEX When Using a No-IP DDNS Key?

Zyxel_Stanley

Question:
DDNS on USG FLEX devices fails when configuring No-IP for WAN redundancy. The DDNS key is entered in the configuration but the update still does not work. What is the cause, and how can this issue be resolved?

Answer:
The issue occurs because the USG FLEX firewall does not support No-IP DDNS key authentication. The device requires the original No-IP account username and password. Using the DDNS key will result in authentication failure and prevent the DDNS hostname from updating.

To resolve the issue:
Use the original No-IP account username and password in the DDNS authentication fields. The DDNS key is not supported.
Verify the “Check public IP URL” setting on the firewall.
The correct value is: https://ipinfo.io/ip

After applying the correct credentials and settings, the DDNS hostname should successfully resolve to the active WAN IP address.