Multiple vBulletin with Single Userbase

[MrD3SAi]

Is it possible to have multiple vBulletin forums share a single userbase? So for example, if someone registers on one of the forums it syncs across the other forums? Or have a single page where they register and that userbase is used for all other forums. Also, single-sign on across all the forums, such as if I sign on one forum, and since the userbase is the same, I am automatically signed into the other forum when I go to it. I know this is a LOT of things I am requesting, but I can see a huge advantage that others might also find it useful.

Thanks again in advance!