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Table Of Contents  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

Previous Topic/Section
IP Addressing Overview and Fundamentals
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Pages in Current Topic/Section
1
2
3
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IP Basic Address Structure and Main Components: Network ID and Host ID
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IP Address Size, Address Space and "Dotted Decimal" Notation
(Page 2 of 3)

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.

Key Concept: IP addresses are 32-bit binary numbers, which can be expressed in binary, hexadecimal or decimal form. Most commonly, they are expressed by dividing the 32 bits into four bytes and converting each to decimal, then separating these numbers with dots to create dotted decimal notation.


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.

 


Previous Topic/Section
IP Addressing Overview and Fundamentals
Previous Page
Pages in Current Topic/Section
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2
3
Next Page
IP Basic Address Structure and Main Components: Network ID and Host ID
Next Topic/Section

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Version 3.0 - Version Date: September 20, 2005

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