Question : Problem: Help with VPN Adtran 850 CSU/DSU

Hello, I am trying to connect three offices together for a mortgage company.  Here is what we have:

1- W2K Server / 20 users
    Adtran total access CSU/DSU (running DHCP - our link to the internet)

2- W2K Server / 10 users
   Same Adtran setup

3- W2K server / 10 users
   This one has another vendors CSU/DSU (also DHCP)

As you can see, I am lost on WAN.  Will the CSU/DSU function like a cable modem / DSL modem, and allow me to use the cheaper router functions like the Linksys / D-Link Cable/DSL routers?

TIA

Answer : Problem: Help with VPN Adtran 850 CSU/DSU

It is true that a CSU/DSU alone will not do what you need here.  However, the Total Access 850 w/ T1 RCU is a CSU/DSU with a built-in router, so I'm going to assume that this is what you're using.  I haven't been able to find anything in the router's documentation stating that it can build VPN tunnels, so let's look at the M$ solution.

If each of these CSU/DSU/RCU (Router Conrol Unit) is connected to the Internet this should be fairly straight forward:

If you're going to be building your VPN using the Win2K servers, then be sure the servers have two NICs.  One of the NICs should have a routable IP address, the other should have a non-routable IP address.  The NIC with the routable IP address should be directly connected to the Adtran's Ethernet port (the IP address you give this NIC should be in the range of IP addresses given to you by your ISP).  The NIC with the non-routable IP address should be directly connected to your private LAN (popular non-routable IP networks are: 10.x.x.x or 192.168.x.x).  Once your IP addresses have been assigned and the servers connected to the routers, you should be able to ping each server's public IP address from the other servers.

Once your servers can ping each other over the Internet, all you have to do is set up RAS so that it makes a server to server connection on each server.  Your Win2K servers should be handling DHCP and NAT, and all your client machines should set the non-routable IP address of the server on their LAN as the default gateway.  Now all your client machines should be able to see the other office networks when the VPN tunnels are working.

Let me know if I need to clarify anything.