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Example 19.2 Change the following IPv4 addresses from dotted-decimalnotation to binary notation. SolutionWe replace^ each^ decimal 19.
number^ with^ its^ binary equivalent (see Appendix B).
Figure 19.3 shows a block of addresses, in both binaryand dotted-decimal notation, granted to a small businessthat needs 16 addresses.We can see that the restrictions are applied to this block.The addresses are contiguous. The number of addresses^4 is a power of 2 (16 = 2 19.
Example 19.5 ), and the first address is divisibleby 16.
- 19-1 IPv4 ADDRESSES An IPv4 address is a 32-bit address that uniquely anduniversally defines the connection of a device (forexample, a computer or a router) to the Internet. Topics discussed in this section: Address SpaceNotationsClassful AddressingClassless AddressingNetwork Address Translation (NAT)19.
- Note An IPv4 address is 32 bits long.19.
- Note The IPv4 addresses are uniqueand universal. 19.
- Note The address space of IPv4 is^32 2 or 4,294,967,296.19.
- Figure 19.1 Dotted-decimal notation and binary notation for an IPv4 address 19.
- Example 19.3 Find the error, if any, in the following IPv4 addresses. 19.
- Note In classful addressing, the addressspace is divided into five classes:A, B, C, D, and E.19.
- Figure 19.2 Finding the classes in binary and dotted-decimal notation 19.
- Example 19.4 Find the class of each address.a. 0 0000001 00001011 00001011 11101111 b. 110 00001 10000011 00011011 11111111 c. 14 .23.120.8 d. 252 .5.15.111Solutiona. 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 Caddress.c. The first byte is 14; the class is A.d. The first byte is 252; the class is E. 19.
- Table 19.1 Number of blocks and block size in classful IPv4 addressing 19.
- Note In classful addressing, a large part of theavailable addresses were wasted.19.
- Table 19.2 Default masks for classful addressing 19.
- Note Classful addressing, which is almostobsolete, is replaced with classlessaddressing. 19.
- Figure 19.3 A block of 16 addresses granted to a small organization 19.
The first address in the block can befound by setting the rightmost^32 −^ 19.
Note n^ bits to 0s.
A block of addresses is granted to a small organization.We know that one of the addresses is 205.16.37.39/28.What is the first address in the block?SolutionThe binary representation of the given address is^11001101 00010000 19.
If we set 32 − 28 rightmost bits to 0, we get^11001101
(^00100101 0010000) or 205.16.37.32.
Example 19.6 This is actually the block shown in Figure 19.3.
