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The TCP/IP Guide  9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)       9  TCP/IP Internet Layer (OSI Network Layer) Protocols            9  Internet Protocol (IP/IPv4, IPng/IPv6) and IP-Related Protocols (IP NAT, IPSec, Mobile IP)                 9  Internet Protocol Version 4 (IP, IPv4)                      9  IP Addressing                           9  IP Addressing Concepts and Issues

IP Addressing Overview and Fundamentals 1 2 3 IP Basic Address Structure and Main Components: Network ID and Host ID

IP Address "Dotted Decimal" Notation

Most people still find hexadecimal a bit difficult to work with. So IP addresses are normally expressed with each octet of 8 bits converted to a decimal number and the octets separated by a period (a “dot”). Thus, the example above would become 227.82.157.177, as shown in Figure 56. This is usually called dotted decimal notation for rather obvious reasons. Each of the octets in an IP address can take on the values from 0 to 255 (not 1 to 256, note!) so the lowest value is theoretically 0.0.0.0 and the highest is 255.255.255.255.

Dotted decimal notation provides a convenient way to work with IP addresses when communicating amongst humans. Never forget that to the computers, the IP address is always a 32-bit binary number; the importance of this will come in when we look at how the IP address is logically divided into components in the next topic, as well as when we examine techniques that manipulate IP addresses, such as subnetting.

Figure 56: IP Address Binary, Hexadecimal and Dotted Decimal Representations

The binary, hexadecimal and decimal representations of an IP address are all equivalent.

IP Addressing Overview and Fundamentals 1 2 3 IP Basic Address Structure and Main Components: Network ID and Host ID

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