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DSL-504T DSL Router User’s Guide
59
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IP Concepts
This appendix describes some basic IP concepts, the TCP/IP addressing scheme and shows how to
assign IP Addresses.
When setting up the Router, you must make sure it has a valid IP address. Even if you will not use
the WAN port (ADSL port), you should, at the very least, make sure the Ethernet LAN port is
assigned a valid IP address. This is required for telnet, in-band SNMP management, and related
functions such as “trap” handling and TFTP firmware download.
IP Addresses
The Internet Protocol (IP) was designed for routing data between network sites all over the world,
and was later adapted for routing data between networks within any site (often referred to as
“subnetworks” or “subnets”). IP includes a system by which a unique number can be assigned to
each of the millions of networks and each of the computers on those networks. Such a number is
called an IP address.
To make IP addresses easy to understand, the originators of IP adopted a system of representation
called “dotted decimal” or “dotted quad” notation. Below are examples of IP addresses written in
this format:
201.202.203.204 189.21.241.56 125.87.0.1
Each of the four values in an IP address is the ordinary decimal (base 10) representation of a value
that a computer can handle using eight “bits” (binary digits — 1s and 0s). The dots are simply
convenient visual separators.
Zeros are often used as placeholders in dotted decimal notation; 189.21.241.56 can therefore also
appear as 189.021.241.056.
IP networks are divided into three classes on the basis of size. A full IP address contains a network
portion and a “host” (device) portion. The network and host portions of the address are different
lengths for different classes of networks, as shown in the table below.