You can think of the Network ports on the Surface and MixRack as being ports on the same network. Ports are provided at both ends simply for convenience, for example, a laptop at FOH for wired control and a wi-fi router on stage for wireless iPad control.
The gigaACE connection links the control network automatically so it doesn’t matter where you physically connect to, just pick the location that works best for you. A common mistake is to patch both MixRack and Surface to the same switch – this will create a network loop.
gigaACE can also run third party control data, so for example, a laptop at the Surface position will be able to ‘see’ and control Ethernet devices connected to the MixRack on stage, such as wireless receivers or remote amplifiers. Provided they are all on the same IP subnet!
For more in-depth information on network ports which might be of interest to your IT guy, have a look at this white paper:
https://www.allen-heath.com/media/AH-dLive-for-IT-managers.pdf