I supposed to cut some customers over to a new T1 internet service. Usually I work with cable or DSL. Nonetheless the carrier (XO) gave me this information and the Cisco 1700 is already powered up and configured.

Here is what they gave me (I X'd out the IP for the sake of the customer)

LAN
Customer LAN Block:X1.4.198.48/29
Customer Gateway:X1.4.198.49
Useable Range: X1.4.198.50 - X1.4.198.54
Customer Subnet mask: 255.255.255.248

WAN
Customer WAN Block: X7.109.159.20/30
Customer Side: X7.109.159.22
Network Side X7.109.159.21
WAN Subnet mask: 255.255.255.252

Ordinarily I do a NAT setup. I see they have given a usable range of 5 addresses. I don't see why they need them (no mail server, no web server etc, I suppose I don't have to use them.

My question:
What is the customer WAN block, Customer Side and Network Side. Why do I need this or do I at all need this stuff?

I am just used to the DNS settings and 1 static IP and it everything works. I don't know what all this is and I just want to be a little literate and confident.

any ideas?

Phone systems for NJ and NY businesses