As far as I can tell, the AddIPAddress api function should still work. AddIPAddress (Compact 2013) | Microsoft Learn
It is something that we have had working in the past, but we’ve used so many modules I can’t remember whether it was this one or a previous one.
@TriUrs: We have not tried that on our side. On CE 6 there was some documentation available describing IP Multihoming. I did not found anything similar for CE 7 or WEC2013, which does not mean it will not work there. For sure, it is not enough to just add the IP address to the registry, as the routing seems not to be automatically updated.