12
Network Layer:
Logical Addressing
41 IPv4 ADDRESSES
An IPv4 address is a 32-bit address that uniquely and universally defines the connection of a device (for example, a computer or a router) to the Internet.
Topics discussed in this section:
Address Space
Notations
Classful Addressing
Classless Addressing
Network Address Translation (NAT)
Note
An IPv4 address is 32 bits long.
The IPv4 addresses are unique and universal.
The address space of IPv4 is
32
2 or 4,294,967,296.
Figure 4.1 Dotted-decimal notation and binary notation for an IPv4 address
Example 4.1
Change the following IPv4 addresses from binary notation to dotted-decimal notation.
Solution
We replace each group of 8 bits with its equivalent decimal number (see Appendix B) and add dots for separation.
Example 4.2
Change the following IPv4 addresses from dotted-decimal notation to binary notation.
Solution
We replace each decimal number with its binary equivalent (see Appendix B).
Example 4.3
Find the error, if any, in the following IPv4 addresses.
Solution
a. There must be no leading zero (045).
b. There can be no more than four group of numbers.
c. Each number needs to be between 0 to 255.
d. A mixture of binary notation and dotted-decimal notation is not allowed.
Note
In classful addressing, the address space is divided into five classes:
A, B, C, D, and E.
Figure 4.2 Finding the classes in binary and dotted-decimal notation
Example 4.4
Find the class of each address.
a. 00000001 00001011 00001011 11101111
b. 11000001 10000011 00011011 11111111
c. 14.23.120.8
d. 252.5.15.111
Solution
a. The first bit is 0. This is a class A address.
b. The first 2 bits are 1; the third bit is 0. This is a class C address. c. The first byte is 14; the class is A.
d. The first byte is 252; the class is E.
Table 4.1 Number of blocks and block size in classful IPv4 addressing
In classful addressing, a large part of the available addresses were wasted. Table4.2 Default Masks for classful
Logical Addressing
41 IPv4 ADDRESSES
An IPv4 address is a 32-bit address that uniquely and universally defines the connection of a device (for example, a computer or a router) to the Internet.
Topics discussed in this section:
Address Space
Notations
Classful Addressing
Classless Addressing
Network Address Translation (NAT)
Note
An IPv4 address is 32 bits long.
The IPv4 addresses are unique and universal.
The address space of IPv4 is
32
2 or 4,294,967,296.
Figure 4.1 Dotted-decimal notation and binary notation for an IPv4 address
Example 4.1
Change the following IPv4 addresses from binary notation to dotted-decimal notation.
Solution
We replace each group of 8 bits with its equivalent decimal number (see Appendix B) and add dots for separation.
Example 4.2
Change the following IPv4 addresses from dotted-decimal notation to binary notation.
Solution
We replace each decimal number with its binary equivalent (see Appendix B).
Example 4.3
Find the error, if any, in the following IPv4 addresses.
Solution
a. There must be no leading zero (045).
b. There can be no more than four group of numbers.
c. Each number needs to be between 0 to 255.
d. A mixture of binary notation and dotted-decimal notation is not allowed.
Note
In classful addressing, the address space is divided into five classes:
A, B, C, D, and E.
Figure 4.2 Finding the classes in binary and dotted-decimal notation
Example 4.4
Find the class of each address.
a. 00000001 00001011 00001011 11101111
b. 11000001 10000011 00011011 11111111
c. 14.23.120.8
d. 252.5.15.111
Solution
a. The first bit is 0. This is a class A address.
b. The first 2 bits are 1; the third bit is 0. This is a class C address. c. The first byte is 14; the class is A.
d. The first byte is 252; the class is E.
Table 4.1 Number of blocks and block size in classful IPv4 addressing
In classful addressing, a large part of the available addresses were wasted. Table4.2 Default Masks for classful