Playing netgames with level packs.

Okay in the case of sonicx8000's netgame, he wanted to play sonic ultima, so I downloaded his level pack, so I could play with the people on sonic ultima, so I download it, and load it in, and i says I have to restart before playing, and when i try to join normal without it installed i get closed out from srb2, is it possible to play certain netgames if they have a level pack loaded into it.

This is also in case I want to play level pack netgames.

Yes, the level automatically adds when you join.