IP address classes – IPv4

Written on by admin on. Posted in Cheat Sheets

IPv4 addresses are 32 bit addresses divided into 4 octets. In this article we’ll examine how IP addresses are divided into classes and what are they used for. Classful allocation of IP address space wasted many addresses, which exhausted the availability of IPv4 addresses. Today is used  classless addressing system.

In next table you see the classification of IPv4 addresses.

IPv4 addresses classification
IP Address Class First octet range (decimal/binary) Octects for Network(N) and Hosts(H) Default subnet mask Nr of possible networks and hosts
A 1-127;
0000000001111111
N.H.H.H 255.0.0.0 126 nets (2^7);
16,277,214 hosts (2^24-2)
B 128-191;
1000000010111111
N.N.H.H 255.255.0.0 16,384 nets (2^14);
65,534 hosts (2^16-2)
C 192-223;
1100000011011111
N.N.N.H 255.255.255.0 2,097,152 nets (2^21);
254 hosts (2^8-2)
D 224-239;
1110000011101111
Not Applicable
E 240-255;
1111000011111111
Not Applicable

Class A

Designet to fit a very large numbers of IP addresses. There are 128 possible networks, from 0.0.0.0/8 to 127.0.0.0/8. It takes one-half of IPv4 addresses pool and uses default mask 255.0.0.0 (/8). Number of ip addresses per network are 224=16,277,216 and for hosts are used 16,277,216-2=16,277,214. First IP address is used as network address and last is broadcast address.

Class B

Designed for medium to large networks. There are 16,384 possible networks, from 128.0.0.0/16 to 191.255.0.0/16 with default mask 255.255.0.0 (/16). Number of ip addresses per network are 214= 65,536 and for hosts are used  65,536-2=65,534.

Class C

This class of addresses is designed for small networks. There are 2,097,152 possible networks, from 192.0.0.0 /24 to 223.255.255.0 /24 with default mask 255.255.255.0 (/24). Number of ip addresses per network are 28= 256 and for hosts are used  256-2=254.

Class D

 Class D block of IP addresses is used for multicast applications such as IPTV.

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Comments (2)

  • WAQUAR YUSUF

    |

    very thanks to u .update more and more materials pllzzzzzzzzzzz.its very nice……….

    Reply

  • Linus

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    good, could you explain subnetting principle which spit /16 to /18 ?

    Reply

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