How to divide IP addresses into categories A, B, and C

Each IP address contains two identifiers: the network ID and the host ID. The Internet Commission defines different types of IP addresses to accommodate networks of different capacities. Generally, users are exposed to three types of IP addresses: A, B, and C. Let's take A look at how classes A, B, and C of IP addresses are divided to better understand their application in the network.

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1. Class A IP address

Class A IP addresses play a crucial role in the Internet, and their unique characteristics make them suitable for large networks with more than 16 million hosts. Let's take A deeper look at the characteristics and application scenarios of Class A IP addresses.

A Class A IP address consists of a one-byte network address and a three-byte host address. The first number is the network number, and the remaining three numbers are the number of the local computer. This allocation results in A large network space for Class A IP addresses, with network numbers ranging from 1.0.0.0 to 126.0.0.0. The IP address 1.0.0.0 is reserved as the local loopback address for local testing and communication.

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Because the Class A IP address network identity occupies only 1 byte, it has about 16.8 million different network addresses. This makes Class A IP addresses particularly suitable for large networks, which can accommodate millions of computers and devices. As A result, Class A IP addresses played a crucial role in the topology of the early days of the Internet, providing a huge network demand for organizations such as large enterprises, government agencies, and global Internet service providers.

Large enterprises and organizations often need to manage A large number of computers, servers and network equipment, and the network space of Class A IP addresses is sufficient to meet their needs. Government agencies need to build A large internal communication network and external service platform, and also need a large-scale network space of Class A IP addresses to meet these needs. Global Internet service providers, on the other hand, need to assign a large number of IP addresses to their users in order to support worldwide Internet access.

2. Class B IP address

Class B IP address is another common type of IP address on the Internet, consisting of a 2-byte network address and a 2-byte host address. In Class B IP addresses, the first two numbers are network numbers and the last two numbers are host numbers. In contrast to Class A IP addresses, Class B network addresses are suitable for medium-size networks, each of which can accommodate more than 60,000 computers.

Class B IP addresses have network numbers ranging from 128.0.0.0 to 191.255.255.255. IP address 255.255.255.255 is reserved as a limited broadcast address and is used to send broadcasts to all hosts in the network. This means that a Class B IP address can be used to broadcast messages to all hosts in a network, facilitating some specific network communication needs.

The network ID of Class B IP addresses is 16 bits long, and the host ID is also 16 bits long. This reduces the network space of Class B IP addresses compared to Class A IP addresses, but it is still enough to meet the needs of medium-sized networks. The characteristics of a Class B IP address make it suitable for medium-sized organizations, schools, and regional Internet service providers.

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Medium-sized organizations typically require a large network scope to connect multiple departments or branches to support internal communication and resource sharing. Class B IP addresses meet this need by providing these organizations with approximately 60,000 + available host addresses, enough to support larger scale networks.

3. Class C IP addresses

A Class C IP address consists of a three-byte network address and a one-byte host address. The first three numbers are network numbers, and the last number is host numbers. Class C network addresses have a large number of addresses and are suitable for small local area networks, each network can contain a maximum of 254 computers.

The network numbers of Class C IP addresses range from 192.0.0.0 to 223.255.255.255. Among them, the IP address 224.0.0.0 is reserved as a multicast address for sending datagrams simultaneously to a group of hosts. Class C IP addresses are typically used in home networks, small business Lans, and small organizations for their relatively small network size.

Classes A, B, and C of IP addresses are applicable to networks of different scales. Class A IP addresses are suitable for large networks with a large number of available hosts; Class B IP addresses are applicable to medium-scale networks with a moderate number of hosts. Class C IP addresses are applicable to small-scale networks with relatively few hosts. Reasonable division of IP address categories helps optimize the network structure and meet the requirements of networks of different scales. In practical applications, choosing the appropriate IP address category according to the network size and requirements will help build a more efficient, secure and stable network environment.