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ZyAIR G-1000 Access Point User’s Guide

IP Subnetting G-1

Appendix G

IP Subnetting

IP Addressing

Routers “route” based on the network number. The router that delivers the data packet to the correct

destination host uses the host ID.

IP Classes

An IP address is made up of four octets (eight bits), written in dotted decimal notation, for example,

192.168.1.1. IP addresses are categorized into different classes. The class of an address depends on the

value of its first octet.

 Class “A” addresses have a 0 in the left most bit. In a class “A” address the first octet is the network

number and the remaining three octets make up the host ID.

 Class “B” addresses have a 1 in the left most bit and a 0 in the next left most bit. In a class “B” address

the first two octets make up the network number and the two remaining octets make up the host ID.

 Class “C” addresses begin (starting from the left) with 1 1 0. In a class “C” address the first three

octets make up the network number and the last octet is the host ID.

 Class “D” addresses begin with 1 1 1 0. Class “D” addresses are used for multicasting. (There is also a

class “E” address. It is reserved for future use.)

Chart 6 Classes of IP Addresses

IP ADDRESS: OCTET 1 OCTET 2 OCTET 3 OCTET 4

Class A 0 Network number Host ID Host ID Host ID

Class B 10 Network number Network number Host ID Host ID

Class C 110 Network number Network number Network number Host ID

Host IDs of all zeros or all ones are not allowed.

Therefore:

 A class “C” network (8 host bits) can have 2

–2 or 254 hosts.

 A class “B” address (16 host bits) can have 2

–2 or 65534 hosts.

1 2 ... 168 169 170 171 172 173 174 175 176 177 178 ... 196 197

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