I would have used external adapters if only because they might want to upgrade to gigabit which uses all 4 pairs. But then again only a hardcore IT geek wants to run gigabit in their house
Truth be told, I mixed 100baseT and POTS telephone in the same cat5 cable for a residential installation I did for a friend of mine (surface wiring, none of it was fished). The IEEE 802.3 specs state that this is acceptable. (It is not acceptable for 100baseT4--was any 100baseT4 equipment actually ever sold?). It works fine. Running another cable was not an option due to the surface wiring.
Actually this is something I've always wanted to test anyway, since armchair electrical engineer wannabees always pontificate that the high ring voltage may interfere with the ethernet signals.
It works fine, but I wouldn't do it that way for anything but a residential installation with those contstraints, where I know that they'll never want to use gigabit ethernet over that cable, and where any potential failure is only going to cause their son's PC to not have internet access. (Not a big deal in the grand scheme of things).
