[USG Flex H - V1.39(ABZH.0)ITS-260800686] - User Custom DDNS effective IP not appear

Maverick87

You're right.

Request submitted

Maverick87

Hello @PeterUK and @Zyxel_Luna,
after opened the ticket on Dynu, this is the reply:

We understand that your interface is discarding the 'nochg' response, which causes your "Effective IP" field to blank out when the IP address hasn't changed.

The response behavior you're seeing follows the standard Dynamic DNS update protocol. The Dynu API returns:
- good <IP> only when the IP address has actually changed and a successful update was performed.
- nochg when the IP address is unchanged, meaning no update was performed.

This design has been in place for many years to align with long-standing DDNS specifications and to ensure efficient API usage. Changing this behavior to always return good <IP> would break compatibility with countless existing routers, devices, and scripts that rely on this standard response format, so we are unable to make that change.

Recommended Workaround:
Your interface should handle the nochg response by retaining the last known IP address rather than clearing the field. If your "Effective IP" field must always show the current registered IP, you can either:
1. Modify your interface to keep the previously stored value when nochg is received.
2. Query a separate status endpoint (if available) to fetch the current IP without triggering an unnecessary update.

So seems that the "nochg" response is a DDNS API Standard response, also if I see that other DDNS services, for the nochg return also the IP (nochg 1.2.3.4).

Anyway, is possible to "save" the effective IP before the update? Then, if the update return "nochg" status, into the effective IP put the previous saved IP.

Zyxel_Luna

Hi @Maverick87 ,

From your screenshot, we noticed that you are currently using the [Auto].

Based on our testing, the Effective IP does not display under [User Custom] mode, as this mode is not specifically designed for the Dynu DDNS mechanism.

However, under [Dynu Basic] mode, the Effective IP displays properly regardless of selecting Interface or Public IP.

We will release a new weekly firmware next week.

After upgrading, you will be able to use [Dynu Basic] mode normally, and the Effective IP will be displayed correctly.

Thank you for your patience and understanding.

Maverick87

Hi @Zyxel_Luna,

Thank you for your reply, but I think is necessary implement a sort of "backup" if the nochg message arrive without the IP.

Anyway, I'll wait the weekly firmware. If you receive the fix, can you tell me so you pass me the weekly firmware?

Thank you