D-Link DI-304, User Manual

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DI-304/DI-304M ISDN Remote Router
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.
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