Understanding IP Abode Classes
Class A—0NNNNNNN.HHHHHHHH.HHHHHHHH.HHHHHHHH
First octet represents the arrangement abode and the actual three octets represent the host
address.
First aerial adjustment bit is set to 0.
7 arrangement bits.
24 host bits.
First byte range: 0–127.
126 Chic A ranges abide (0 and 127 are reserved).
16,777,214 hosts are on anniversary Chic A.
Example: Host 10.0.0.1 on arrangement 10.0.0.0
Class B—10NNNNNN.NNNNNNNN.HHHHHHHH.HHHHHHHH
First two octets represent the arrangement abode and the actual two octets represent the host
address.
First two aerial adjustment $.25 are set to 1 and 0, respectively.
14 arrangement bits.
16 host bits.
First byte range: 128–191.
16,384 Chic B ranges exist.
65,532 hosts are on anniversary Chic B.
Example: Host 128.10.1.5 on arrangement 128.10.0.0
Class C—110NNNNN.NNNNNNNN.NNNNNNNN.HHHHHHHH
First three octets represent the arrangement address, and the actual octet represents the host
address.
First three high-order $.25 are set to 1, 1, and 0, respectively.
21 arrangement bits.
8 host bits.
First byte range: 192–223.
2,097,152 Chic C ranges exist.
254 hosts are on anniversary Chic C.
Example: Host 192.15.1.1 on arrangement 192.15.1.0
Class D—1110MMMM.MMMMMMMM.MMMMMMMM.MMMMMMMM
Mainly aloof as multicast addresses.
First four high-order $.25 are set to 1, 1, 1, and 0, respectively.
28 multicast abode bits.
First byte range: 224–247 (first octet of a Chic D abode has a minimum amount of 224 and a
maximum amount of 239).
Class D ambit is acclimated for multicast addresses—see RFC 1112.
Example: 225.1.100.100
Class E—1111RRRR.RRRRRRRR.RRRRRRRR.RRRRRRRR
Mainly aloof for beginning and approaching use.
First four aerial $.25 are set to 1, 1, 1, and 1, respectively.
28 aloof abode bits.
First byte range: 248–255 (first octet of a Chic E abode starts with 240).
In accession to actuality acclimated for experimentation, Chic E addresses are aloof for approaching use.
Note
N denotes the arrangement ID bits.
H denotes the host ID bits.
M denotes the multicast abode bits.
R denotes the aloof bits.
The chic of an IP abode can be accustomed from the aboriginal four $.25 of the aboriginal byte of the IP address. The
value of the aboriginal octet in the IP abode resolves to the chic aural the ambit of which the IP abode falls.
Table 2-1 summarizes the accessible ambit of IP addresses for the altered IP abode classes that were
previously discussed.
Table 2-1. Ambit of IP Addresses per Class
Class Accessible Ambit of Addresses
A 0.0.0.0 through 127.255.255.255
B 128.0.0.0 through 191.255.255.255
C 192.0.0.0 through 223.255.255.255
D 224.0.0.0 through 239.255.255.255
E 240.0.0.0 through 247.255.255.255
Table 2-2 shows the best cardinal of networks and hosts that can be acquired aural anniversary class.
Table 2-2. Networks and Hosts per Class
Class Max Cardinal of Networks Max Cardinal of Hosts per Network
A 126 (2^7–2) 16777214 (2^24–2)
B 16384 (2^14) 65534 (2^16–2)
C 2097152 (2^21) 254 (2^8–2)
D — —
E — —
Note
Class A—The best cardinal of networks is bargain by 2 to annual for the aloof arrangement IP
address of 0.xxx.xxx.xxx and 127.xxx.xxx.xxx.
The best cardinal of hosts per arrangement is additionally bargain by 2 to annual for the aloof host IP
address in which all the host ID abode $.25 are either 1 or 0—that is, the arrangement abode and the
broadcast address.