OK..your core router is the 2610....you will need the second router int order to utilize your ip space. I would look into upgrading from the 678 to something like the 827 series. There are a few choices for this router so make sure you get the right type. You will then also need an unmanaged switch. You would then configure that router to connect to your DMT dsl circuit with the first ip routeable on the ethernet port. Then connect this to your switch. Then the switch to the 2610 ethernet which would then use the second ip routeable with the default gateway being the next hop router ip address. This will give you the ports to connect ip routable devices such as mail servers and others directly on the internet by connecting them to your switch. Or you could just connect it right now with a crossover cable to one of your ethernet ports and we can test from there. We know that the IP address on the 678 is:
IP Port Address = 00, 71.32.228.190
IP Port Address Mask = 00, 255.255.255.224
Subnet details:
# Exported from Advanced Subnet Calculator
# 3/20/2005 1:27:08 AM
#
Subnet Mask Subnet Size Host Range Broadcast
71.32.228.160 255.255.255.224 30 71.32.228.161 to 71.32.228.190 71.32.228.191
The ip address is one less than the broadcast address so you can use any from .161 to .189 on the ethernet port.
Gotta call it a night....talk more tomorrow....wait it already is tomorrow....
If you are happy with help so far maybe throw a * my way...
See Ya