Fraghouse Invasion works online fully without any hitches, but it is recommended that you follow this chart for bandwidth recommendations. The bandwidth amount and player amount are recommended settings using the default FHI settings - you may be able to host more/fewer comfortably by adjusting Max Monsters Per Player or adjusting the monsters.
28k upload - 3 players 38k - 4-5 players T1 - 6-8 players T3 - 16 players 100MBit - 24 players or more
Setting up a server for FHI2k4 is easy. You do not need to mess around with ServerPackages because they will auto-generate when you start up the mod for the first time. If you are running Windows you can use the Host Game GUI to launch either a listen or dedicated server. Webadmin and MapVote are enabled by default. If you run Linux, assuming you know how to use a command line, you can use this UCC syntax from your UT2004/System/ folder:
ucc server FHI-Mapname.ut2 -log=FHI2k4Server.log -mod=FHI2k4
The last parameter is of course important. That's all you need to know about setting up a server. Windows users have an easy ride to configuring settings from the GUI too.