What are the categories of IP addresses?

IP addresses are divided into 5 categories: 1. Class A address refers to the four-segment number of the IP address, the first segment of the number is the network number, and the remaining three segments of the number are the local computer number; 2. Class B address means that among the four numbers in the IP address, the first two numbers are the network number; 3. Class C address means that among the four numbers in the IP address, the first three numbers are the network number. The remaining number is the number of the local computer; 4. Class D address, whose first byte starts with "1110", is a specially reserved address; 5. Class E address, starts with "1111".

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

IP address (Internet Protocol Address) refers to the Internet Protocol address, also translated as Internet Protocol address.

The IP address is a unified address format provided by the IP protocol. It assigns a logical address to each network and each host on the Internet to shield the differences in physical addresses.

IP addresses are divided into 5 categories: Class A, Class B, Class C, Class D, and Class E.

When the Internet was originally designed, in order to facilitate addressing and hierarchical network construction, each IP address included two identification codes (ID), namely the network ID and the host ID. All hosts on the same physical network use the same network ID. A host on the network (including workstations, servers, etc.) on the network has a host ID corresponding to it. The Internet Committee has defined 5 IP address types to suit networks of different capacities, namely Class A ~ Class E.

Among them, categories A, B, and C3 (table below) are uniformly allocated globally by InternetNIC, and categories D and E are special addresses.

##B16384(2^14)128.0.0.1-191.255.255.25465534172.16.0.0-172.31.255.255C2097152(2^21)192.0.0.1-223.255.255.254254

Class A IP address

A Class A IP address means that among the four numbers in the IP address, the first number is the network number, and the remaining three numbers are is the number of the local computer. If the IP address is represented in binary, the Class A IP address consists of a 1-byte network address and a 3-byte host address. The highest bit of the network address must be "0". The length of the network identifier in a Class A IP address is 8 bits, and the length of the host identifier is 24 bits. The number of Class A network addresses is relatively small, with 126 networks, and each network can accommodate more than 16 million hosts.

Class A IP address address range 1.0.0.1 to 127.255.255.254 (binary representation: 00000001 00000000 00000000 00000001 - 01111111 11111111 11111111 11111110). The last one is the broadcast address.

Class B IP address

A Class B IP address means that among the four numbers in the IP address, the first two numbers are network numbers. If the IP address is represented in binary, the Class B IP address consists of a 2-byte network address and a 2-byte host address. The highest bit of the network address must be "10". The length of the network identifier in the Class B IP address is 16 bits, and the length of the host identifier is 16 bits. Class B network addresses are suitable for medium-sized networks. There are 16,384 networks, and each network can accommodate more than 60,000 computers. tower.

Class B IP address range 128.0.0.1-191.255.255.254 (binary representation: 10000000 00000000 00000000 00000001----10111111 11111111 11111111 11111110). The last one is the broadcast address.

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

Class C IP address

A Class C IP address means that among the four numbers in the IP address, the first three numbers are network numbers, and the remaining A number is the number of the local computer. If the IP address is represented in binary, the Class C IP address consists of a 3-byte network address and a 1-byte host address. The highest bit of the network address must be "110". The length of the network identifier in a Class C IP address is 24 bits, and the length of the host identifier is 8 bits. There are more Class C network addresses, with more than 2.09 million networks. Suitable for small-scale local area networks, each network can only contain up to 254 computers.

Class C IP address range 192.0.0.1-223.255.255.254 (binary representation is: 11000000 00000000 00000000 00000001 - 11011111 11111111 11111111 11111110).

The subnet mask of Class C IP address is 255.255.255.0, and the maximum number of hosts supported by each network is 256-2=254

Class D IP address

Class D IP address, the first byte starts with "1110", which is a specially reserved address.

Class D IP addresses were historically called multicast addresses, that is, multicast addresses. In Ethernet, a multicast address names a set of stations on the network that should receive a packet. The highest bit of the multicast address must be "1110", ranging from 224.0.0.0 to 239.255.255.255.

Class E IP address

Class E IP address starts with "1111", and its first byte range is 240~255, reserved for future use .

Among them, 240.0.0.0~255.255.255.254 is the reserved address and 255.255.255.255 is the broadcast address.

For more related knowledge, please visit the FAQ column!

Category	Maximum number of networks	IP address range	Maximum number of hosts in a single network segment	Private IP address range
A	126(2^7-2)	1.0.0.1-127.255.255.254	16777214	##10.0.0.0-10.255.255.255
			##192.168.0.0-192.168.255.255

The above is the detailed content of What are the categories of IP addresses?. For more information, please follow other related articles on the PHP Chinese website!