I unplugged ethernet from the master today as a test assuming the backup would take over osc responsibilities. I'm using touchosc and oscrfr, neither one worked. All the same port/enabled, etc settings as on the master. Oscrfr just says "Please enable osc in eos>setup>show control." It is already enabled, so no help there. I changed the host ip address to the backup address in touchosc.
This happens because the IP address of your backup is not the same as the master. You must establish a new connection with the IP of the backup. Maybe broadcasting helps (e.g. 10.101.1.255).
Adding to what sstaub says, if touchosc and oscrfr rely only on UDP for communication with Eos, using Broadcast should work so long as your Primary and Backup are on the same subnet for the network your touchosc / oscrfr device(s) are using. They might be:
10.101.93.101, 255.255.0.0 and 10.101.93.102, 255.255.0.0
However, I think OSCRFR uses a TCP connection - in that case you must specify the Eos console's IP address, and you can probably only specify one address at a time.
Something like GitHub - ETCLabs/OSCRouter: UNOFFICIAL - Simple UDP/TCP packet router for Mac and Windows, with optional OSC specific options might be usably to create connections at both consoles from one controlling device. Keep in mind that the Backup will not act on OSC messages (whether UDP or TCP) until it has Taken Control.
It appears, nobody read the last line of my post. The backup took control, then I changed the ip address that my tablet app (touchosc) points to, and set it as the backup console's ip address. In 2.9.x when this occured, the backup would accept and send osc commands as if it was the Primary (until the Primary shows back up on the network) and the show continues. In 3.0, I can't communicate with the backup.
I apologize, I misunderstood what was meant by "host IP address".
Are you using the same showfile in v3.0 as v2.9 for testing? If you quit the Backup to the Welcome Screen, then start as Primary, does touchosc work then?
I'm sorry everyone. One console had the "Backup automatically takes control" box checked, and the other one didn't. Osc does in fact work as expected on the backup when it takes control.