If you want to be able to run the Ulterra from either the bow or the stern, you are also going to have to get the Ethernet connection to both places. I think the best way to do this is to have an Ethernet switch (
Humminbird | AS ETH 5PXG )set up at the console. You would run an the Ethernet for the Ulterra to it, an Ethernet for the bow unit, and an Ethernet for the stern or console location.
You also need to think about how you are going to do your power connections. I don't know what your boat has for onboard power wiring, but you don't want to use that for your power to your units. You want to set up your own power circuit tied directly to the cranking battery.
I would run 1
2 ga wire to a dedicated Bluesea 5025 fuse box under the console. The console or stern unit will wire straight to the 5025. I would use separate circuits from the 5025 to the bow unit and Ethernet switch, with a shutoff switch mounted to kill the Ethernet switch (you don't want it to run your battery down while sitting.) I would use 12 ga throughout.......That may seem like overkill, but you will have less voltage drop issues.....Actually I would probably use 10 ga to the blue sea and 12 for everything else.....but that's just me.
Put a 20 amp fuse in the hot wire close to the starting battery. The rest will be fused in the 5025 with appropriate fuses for the units and Ethernet switch.
When I run power wiring in my boat, I also make sure I use twisted pair wire. The twisted wire wire help eliminate interference from other sources. If you don't want to buy twisted wire, you can easily twist it yourself......just tie one end of the wires to something solid, chuck the other end into a drill, pull it tight and run the drill to twist the wires together.
The cost starts adding up to get the Ethernet and power and transducers to multiple locations.