During undergrad in the US we used to use Xbox connect. It would function had a lan bridge to other people so you'd just use the regular halo UI to find a game.
So it has no real online features but they were grafed on by a bunch of tricks.
Ah Xbox connect. Had mine and my brother's xbox on the same switch so we could play together with others.
We used to connect across the Atlantic to a host in the US, dude had a fat fibre pipe so 16 player Halo 2 with 0 lag and modded features (like spawning a warthog for each player in blood gulch for Cat vs. Mouse games.)
Fun times. Halo 3 iirc made some changes to the netstack to break it though :(
So it has no real online features but they were grafed on by a bunch of tricks.