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SpeedTouch 210i 
 
68 
Appendix B – Basic IP Concepts 
This appendix describes some basic IP concepts, the TCP/IP addressing scheme and 
show how to assign IP Addresses.  
 
When setting up the router, you must make sure all ports to be utilized on the router have 
valid IP addresses. Even if you will not use the ISDN or WAN ports, you should, at the 
very least, make sure the 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 to allow routing between networks (often referred to as 
“subnets”) within any site. 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.