more specifically, MacOS 10.5. I realize this question is out of left field, and might be a stab in the dark to ask on this board, but I'm just not finding an answer:

Anyone know how (either using GUI or CLI or downloadable GUI app) to set it so that an application only uses a certain network interface? So let's say I want traffic on port 80 to only use ethernet, and maybe port 23 to only use wireless? That is to say, I don't necessarily need to follow that example above, but seeing how to do that might set me in the right direction.

Thanks.

Dude, I've been looking for that same answer. I assume for the same reasons. You don't want your gaming or download traffic to touch one network connection. I can't find anything on it. I've even tried in VMware Fusion to dedicate a NIC to it. Maybe in Parallels you can do it. Then you can install MacOS or Windows in the VM, let it have one NIC for doing work on, then use the other NIC for other stuff. I don't have parallels though. Let me know if you get this working.