IP Addresses

IP addresses are 32 bits long; like all network-level addresses, they have a network portion and a host portion. The network portion uniquely identifies the data link (that is, the network) and is common to all devices attached to the network. The host portion uniquely identifies a particular device attached to the network.

There are several ways to represent the 32 bits of an IP address. For instance, the 32-bit IP address 00001010110101100101011110000011 could be represented in decimal as 181,819,267.

The binary format is cumbersome, and the decimal format is time-consuming to calculate. A better format is shown in Figure 2.9. The 32 bits of the address comprise four octets, each of which can be represented with a decimal number between 0 and 255, with dots between the decimal representations. In the figure, the 32-bit address is mapped into a dotted-decimal representation.

Figure 2.9. The dotted-decimal format is a convenient way to write IP addresses, but it should not be confused with what the router (or host) sees—a 32-bit string.

00001010110101100101011110000011

Figure 2.9. The dotted-decimal format is a convenient way to write IP addresses, but it should not be confused with what the router (or host) sees—a 32-bit string.

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