Asterisk 101

Hi lads,

Im wondering how this system works. Currently I use debian to run the ISP for everything other than windows web hosting. What im needing to know is this:

How is the asterisk box setup. IE; does it sit in the corner with X amount of modems per phone lines in, and then forward to IP phones over the network/internet for forwards.

What sort of bandwidth will it use. The box will have 1000mb to a 1000mb switch, and from there 100mb to the cubicals. Will this suffice.

When a staff member phones out, it will use the local phone system, not voip (unless to the office in another town). How easy is this to setup?

Many thanks for the help.

Jason Broadhurst