We have a managed T1 line here. I wasn't in IT when it was installed, so I am trying to catch up. Here is a rough diagram I made up of the hardware we have: I have a few questions. First, the reason I am even looking into all of this is to determine how to disconnect the incoming T1 line when I set up our new server. From what I read, it is recommended unhooking the internet where it comes in rather than where it connects to the network. Second, what exactly do all of these boxes do? I know the PIX box is our hardware firewall, but for the rest I am a little unsure. We also used to have a VPN to our sister plant in another state, but we shut that off a few years ago. I have read what the CSU/DSU do. I am assuming the modem is for remote access to the PIX box.