I was on a recent tour and my dimmer tech setup our data rack (we run our data rack on stage) with the DP8000 Artnet & Hognet outputs going through the same 10/100 switch, run as Hognet from F.O.H into switch then out to DP8000 he then run from the DP artnet output through the same switch then off to Video world, I personally would have thought there would have been a conflict but it worked fine and meant it was easier to switch the artnet between the A/B system without digging around in the back of the rack, is this a bad thing to do and can it cause any problems?
This can indeed cause issues for the DP8000 if the fixture link port and the hog net port are addressed in a similar address space which will result in the Art-net simply not working but it sounds like the address space you used was unique to both Hog-net and Art-net which should be fine.
