Nah I've defintely played 2 through a direct IP connection, 2 friends and I used to play it a lot (and with only the one original copy at that) and I'm certain we weren't going through remote servers, if for no reason other than it was 56k & that would have made it all laggy
(I already replied to this once, but the forum software apparently ate it. Arglebeh!)
I just started it up to check, and the only two options are NovaWorld, which is just a server browser, and LAN/IPX.
You can host your own game, but for anyone to find it, they have to connect to the master server, and get the big list o' servers. If it ever had the option to enter an IP address to join, it's since been patched out (I'm using the 10th Anniversary Collection version).
I just discovered that DF1 will let you play over a serial link. How quaint!
Anyone know for sure if the Delta Force servers are dead ?
I'm convinced they got shut down years ago, so surely this means all those games are affectively single player only (even though STEAM advertise them as online).
The master servers for matchmaking are still online, even for DF1 and DF2.