IP Address Classification

When the internetwork was originally designed for easy addressing and hierarchical construction of the network, each IP address consisted of two identification codes (IDS), the network ID and the host ID. All hosts on the same physical network use the same network ID, and one host on the network (including workstations on the network, servers, routers, etc.) has a host ID corresponding to it. The Internet Commission defines 5 types of IP addresses to suit different capacity networks, a class ~e class.

Where a, B, C3 class (the following table) by the internetnic in the global distribution, D, E class is a special address.

category	maximum network number	IP address range	Maximum number of hosts	Private IP address range
A	126 (2^7-2)	0.0.0.0-127.255.255.255	16777214	10.0.0.0-10.255.255.255
B	16384 (2^14)	128.0.0.0-191.255.255.255	65534	172.16.0.0-172.31.255.255
C	2097152 (2^21)	192.0.0.0-223.255.255.255	254	192.168.0.0-192.168.255.255

Class A IP address

A Class A IP address refers to the IP address of the four segment number, the first paragraph number is the network number, the remaining three segment number is the local computer number. If the IP address is represented by a binary, the Class A IP address consists of a 1-byte network address and a 3-byte host address, and the highest bit of the network address must be "0". The identity length of the network in Class A IP address is 8 bits, the length of the host identity is 24 bits, the Class A network address is small, there are 126 networks, each network can accommodate the number of hosts up to more than 16 million units.

Class A IP address range 1.0.0.0 to 127.255.255.255[1] (binary representation: 00000001 00000000 00000000 00000000-01111110 11111111 11111111 11111111). The last one is the broadcast address.

The subnet mask for Class A IP addresses is 255.0.0.0, the maximum number of hosts per network supported is 256 of 3 -2=16777214.

[2]

Class B IP Address

A class B IP address means that in the four segment number of the IP address, the first two numbers are network numbers. If the IP address is represented by a binary, the Class B IP address consists of a 2-byte network address and a 2-byte host address, and the highest bit of the network address must be "10". The identity length of the network in class B IP address is 16 bits, the length of the host identity is 16 bits, the Class B network address is suitable for medium-sized network, there are 16,384 networks, each network can hold more than 60,000 machines.

Class B IP address range 128.0.0.0-191.255.255.255[3] (binary representation: 10000000 00000000 00000000 00000000----10111111 11111111 11111111 11111111). The last one is the broadcast address.

The subnet mask for Class B IP addresses is 255.255.0.0, and the maximum number of hosts supported by each network is 256 of 2 square -2=65534.

Class C IP Address

A class C IP address refers to the IP address of the four-segment number, the first three segments of the number is the network number, the remaining part of the number is the local computer number. If the IP address is represented by a binary, the class C IP address consists of a 3-byte network address and a 1-byte host address, and the highest bit of the network address must be "110". The identity length of the network in class C IP address is 24 bits, the length of host ID is 8 bits, the number of C network address is more, there are more than 2.09 million networks. Applies to small-scale local area networks, which can contain up to 254 computers per network.

Class C IP address range 192.0.0.0-223.255.255.255[3] (binary representation: 11000000 00000000 00000000 00000000-11011111 11111111 11111111 11111111).

The subnet mask for Class C IP addresses is 255.255.255.0, the maximum number of hosts supported per network is 256-2=254

Class D IP Address

The Class D IP address is historically called the multicast address (multicast address), which is the multicast addresses. In Ethernet, the multicast address names a set of sites that should be applied in this network to receive a grouping. The highest bit of the multicast address must be "1110", ranging from 224.0.0.0 to 239.255.255.255.

Special URLs

1. Each byte is a 0 address ("0.0.0.0") corresponding to the current host;
2. Each byte in the IP address is a 1 IP address ("255". 255. 255. 255 ") is the broadcast address of the current subnet;
3. The IP address of the class E IP address that begins with "11110" is reserved for future and experimental use.
4. The IP address cannot begin with the decimal "127", the number 127 in the class address. 0. 0. 1 to 127. 255. 255. 255 for the loop test, such as: 127.0.0.1 can represent the native IP address, with "http://127.0.0.1" can be used to test the local configuration of the Web server.

5. The first 8-bit group of the network ID cannot be fully set to "0", and all "0" represents the local network.

IP Address Classification