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IP address classification (A, B, C, D, E)

The IP address consists of four segments, each field is one byte, 8 bits, and the maximum value is 255

The IP address consists of two parts, the network address and the host address. The network address indicates which network it belongs to, and the host address indicates which host it belongs to. The two are master-slave relationship.

The four types of IP addresses identify a host in the network. The address length of IPv4 is 32 bits, a total of 4 bytes, but in practice we use dotted decimal notation.

According to the network number and host number, IP addresses are divided into three categories A, B, C and special addresses D and E. All zeros and all ones are reserved.

Class A: (1.0.0.0-126.0.0.0) default subnet mask: 255.0.0.0 Private address: 10.0.0.1-10.255.255.254

The first byte is the network number, and the last three bytes are the host number. The IP address of this class is preceded by "0", so the network number of the address is between 1 and 126. It is generally used in large networks. The loopback address 127.0.0.1 is used for test use. For example: ping 127.0.0.1 to test whether the native TCP/IP is normal.

Class B: (128.1.0.0-191.255.0.0) default subnet mask: 255.255.0.0 Private address: 172.16.0.1-172.31.255.254

The first two bytes are the network number and the last two bytes are the host number. The IP address of this class is preceded by "10", so the network number of the address is between 128 and 191. It is generally used in medium-sized networks. 128.0.0.0 is not assigned, and the lowest class B network address that can be assigned is 128.1.0.0

Class C: (192.0.1.0-223.255.255.0) default subnet mask: 255.255.255.0 Private address: 192.168.0.1-192.168.255.254

The first three bytes are the network number and the last byte is the host number. The first IP address of this class is "110", so the network number of the address is between 192 and 223. It is generally used in small networks. 192.0.0.0 is not assigned, and the minimum class C network address that can be assigned is 192.0.1.0

Class D: is a multicast address. The first IP address of this class is "1110", so the network number of the address is between 224 and 239. It is generally used for multicasting users.

Class E: is a reserved address. The IP address of this class is preceded by "1111", so the network number of the address is between 240 and 255.

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