I currently have mobile users who use software installed on their PCs that connects to our server using our external WAN IP and port forwarding.
The router connecting to the server has a backup internet line from a separate ISP.
Currently, if the internet goes down, I need to log into each mobile client and reconfigure the software to connect using the backup WAN IP.
I haven't had to do this yet, but don't want to in the future.
The software can use either a Hostname or IP.
If I configure the software to use a Hostname, is there a way to configure DNS to point to the primary WAN IP, but when it is down, switch to the backup WAN IP?
Or would I be stuck with setting it up with a short TTL and changing it manually when the connection is down.