Lecture 11: The IP Protocol #1

IP Subnetting

Where Class-B networks (and, nowadays, class C also) are in use, the host part of the address is commonly split, for management purposes, to allow subnetting -- typically this involves defining 254 subnets each of 254 hosts. Each of these subnets behaves, for all intents, like an independent class-C network: thus:

Exactly which bits of the subnetted address are used for the network/subnet part and the host part is defined using an address mask, or netmask thus:

255.255.255.0

This says that 24 bits of the address are to be interpreted as "network part". For example, at Bendigo the "ironbark" UNIX system address is:

Address = 149.144.21.60 Netmask = 255.255.255.0

Thus ironbark is addressed as:

class B network: 149.144
subnet: 21
host number: 60

Lecture 11: The IP Protocol #1

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