A Vanilla server is not the same as Classic. A Vanilla server does not allow certain functions of the ISBoxer Addon to work correctly, that you might find rather handy if it did (the Assist and Follow commands are the main pieces). With a Vanilla setup, which is old school select target, follow/assist target, (e.g. F1, F2, F3, to select party member, some other key for Follow/Assist) will work on Classic, but it just wont have the same panache of the Addon, and usually will mean that to auto assist means you need to press hotkeys twice to get things to function in combat.