IP Address Classification (Classes A,B,C,D,and E) - Huawei Enterprise Support Community

IP Address Classification (Classes A, B, C, D, and E)

Created: Mar 4, 2020 06:53:00Latest reply: Jan 29, 2022 05:25:49 1339 10 5 0 0

Hello, dear friends!

Today, I'd like to share my knowledge about IP address classification with you. Let's discuss and learn about it.

An IP address consists of four segments. Each field is one byte and has eight bits. The maximum value is 255.

An IP address consists of a network address and a host address. The network address indicates the network to which the host belongs, and the host address indicates the host to which the host belongs. The two nodes are in the master-slave relationship.

The four types of IP addresses identify a host on the network. An IPv4 address is 32 bits long and has four bytes. In practice, however, the IPv4 address is expressed in dotted decimal notation.

Class A

Network ID(7 bits)

Host ID (24 bits)

Class B

Network ID(14 bits)

Host ID (16 bits)

Class C

Network ID(21 bits)

Host ID (8 bits)

Class D

Multicast group ID（28 bits）

Class E

To be reserved for future use（27 bits）

P addresses are classified into three types (A, B, and C) and special addresses (D and E) based on network IDs and host IDs.

All 0s and all 1s are reserved.

Class A: (1.0.0.0-126.0.0.0) (default subnet mask: 255.0.0.0 or 0xFF000000). The first byte is the network ID, and the last three bytes are the host ID. The first digit of an IP address of this type is 0. Therefore, the network ID of the IP address ranges from 1 to 126. It is generally used on large-scale networks.

Class B: (128.0.0.0-191.255.0.0) (default subnet mask: 255.255.0.0 or 0xFFFF0000). The first two bytes are the network ID, and the last two bytes are the host ID. The network ID of the IP address ranges from 128 to 191 because the first digit of the IP address is 10. It is generally used on medium-scale networks.

Class C: (192.0.0.0-223.255.255.0) (subnet mask: 255.255.255.0 or 0xFFFFFF00). The first three bytes are the network ID, and the last byte is the host ID. The prefix of the IP address is 110. Therefore, the network ID of the IP address ranges from 192 to 223. It is generally used on small-scale networks.

Class D: multicast address. This type of IP address starts with 1110. Therefore, the network ID ranges from 224 to 239. Generally, this parameter is set to 1 for a multi-channel broadcast user.

Class E: reserved address. The network ID of an IP address of this type ranges from 240 to 255 because the first digit of the IP address is 1111.

Among the three major types of IP addresses, three areas are reserved as private addresses. The address ranges are as follows:

Class A address: 10.0.0.0～10.255.255.255

Class B addresses: 172.16.0.0～172.31.255.255

Return address: 127.0.0.1. It is also the IP address of the local host, which is equivalent to the localhost or IP address of the local host. Generally, this parameter is used for tests. For example, run the ping 127.0.0.1 command to check whether the TCP/IP connection is normal.