WAN1 is my fixed landline. WAN2 is my sim based backup line (using external router).

WAN2 is set up to Failover when WAN1 fails.

I have a subdomain that needs to be set to the WAN1 IP when its active and it needs to be switched to point to a specific IP (195... not WAN2) if WAN2 is active. If neither is active then there should not be any change to the subdomain.

I have set index 1 to WAN1 Only with the Service IP set to .....&ip=###IP###

I have set index 2 to WAN2 Only with the Service IP set to .....&ip=195.....

Is this the correct way to do it?

I assume that updates will only happen when the status of either WAN changes.