Above is partially incorrect, brain fade. More specifically, you bridge to a second ethernet port in order to split server and streamer duty. Most servers have only a single ethernet port, usb out to dac or usb renderers, perhaps I2S, spdif, etc.
Adding the second ethernet port has two advantages, possibly three, the first as above is to separate streamer. The second is one can than convert to fiber post server, galvanic isolation. Dedicated streamers can also be superior to built in streamer in some servers. The third possible advantage is usb out on server/streamer may be inferior to streamer usb, many streamers make extra efforts in providing superior usb out, such as femto clocks, superior grounding, etc.
In the above cases, one assigns the port they choose as ethernet port and then provide usb to ethernet conversion cable. In may case being Mac, thunderbolt to ethernet cable.
This was major upgrade for me, right up there with LPS and fiber conversion.