P-660HW-T v2 User’s Guide

APPENDIX H

IP Addresses and Subnetting

This appendix introduces IP addresses, IP address classes and subnet masks. You use subnet masks to subdivide a network into smaller logical networks.

Introduction to IP Addresses

An IP address has two parts: the network number and the host ID. Routers use the network number to send packets to the correct network, while the host ID identifies a single device on the network.

An IP address is made up of four octets, written in dotted decimal notation, for example, 192.168.1.1. (An octet is an 8-digit binary number. Therefore, each octet has a possible range of 00000000 to 11111111 in binary, or 0 to 255 in decimal.)

There are several classes of IP addresses. The first network number (192 in the above example) defines the class of IP address. These are defined as follows:

•Class A: 0 to 127

•Class B: 128 to 191

•Class C: 192 to 223

•Class D: 224 to 239

•Class E: 240 to 255

IP Address Classes and Hosts

The class of an IP address determines the number of hosts you can have on your network.

•In a class A address the first octet is the network number, and the remaining three octets are the host ID.

•In a class B address the first two octets make up the network number, and the two remaining octets make up the host ID.

•In a class C address the first three octets make up the network number, and the last octet is the host ID.

Appendix H IP Addresses and Subnetting

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