Dynamic DNS when my WAN address is private and thus does not change

[Medicineman25]

I have the usual home setup with an OPNSense appliance sitting behind a consumer grade router provided by my ISP. How do I configure DynDNS in this setup? Does anything change?

Here is the error I'm getting:

/services_dyndns_edit.php: Dynamic DNS (<address>) There was an error trying to determine the public IP for interface - wan(igb2). Probably interface is not a WAN interface.

Surely not... surely given that most dynamic dns clients can easily update from well behind a public interface that this shouldn't be an issue for opnsense.

EDIT: turns out this is indeed a limitation of using opnsense in the home, or rather of using it in this configuration. As an alternative, ddclient can easily be spun up in docker and tbh is the preferred method.

[jezza007]

If you have recently updated Opnsense to 22.1 it advise that the dyndns plugin will be deprecated in the next release and in favour to install ddclient on opnsense

What you have not mentioned is how your opnsense WAN interface is setup with your ISP router, bridge mode or have you put the opnsense WAN interface into the DMZ of the ISP router?
Given the error message it sounds like bridge mode in which case the WAN interface of Opnsense can only talk to the ISP router and therefore does not know the external IP address and Dynamic DNS would have to be configured on the ISP router.

If the WAN interface of Opnsense has been exposed to the Internet by putting into the DMZ then it will know the external public IP address and you can use ddclient or DynDns on Opnsense and configure to make Dynamic updates of the public IP address to your chosen Dynamic IP provider DynDNs or whomever