IP classification Address How the--a,b,c class is divided

Today the IP network uses 32-bit addresses, dotted decimal format, such as 172.16.0.0. Address format: IP address = Network address + host address or IP address = host address + subnet address + host address.

IP Address Type

When the internet was originally designed, in order to facilitate the network's addressing and layering structure, all IPs contained two identifiers (IDs). That is, the network ID and 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 IP address is divided into 5 types depending on the network ID. Class A addresses, Class B addresses, Class C addresses, Class D addresses, and class E addresses.
1. Class A IP address

A 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" and the address range is from 1.0.0.0 to 126.0.0.0. There are 126 available Class A networks, each of which can hold more than 100 million hosts.

2. Class B IP Address

A 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", and the address range is from 128.0.0.0 to 191.255.255.255. There are 16,382 available Class B networks, each of which can hold more than 60,000 hosts.

3. Class C IP Address

A 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". range from 192.0.0.0 to 223.255.255.255. Class C network can reach more than 2.09 million. Each network can hold 254 hosts.

4. Class D addresses are used for multipoint broadcasts (multicast).

Class D IP address the first byte starts with "Lll0", which is a specially reserved address. It does not point to a specific network. This type of address is now used in multipoint broadcasts (multicast). Multicast addresses are used to address a group of computers at a time. It identifies a group of computers that share the same protocol.

5. Class E IP Address

Start with "Llll0". Use reservations for the future.

Full 0 ("0. 0. 0. 0 ") address corresponds to the current host. Full "1" IP address ("255". 255. 255. 255 ") is the broadcast address of the current subnet.

Of the 3 main types of IP addresses, 3 zones are reserved as private addresses, and their address ranges are as follows:

Class A address: 10.0.0.0~10.255.255.255

Class B Address: 172.16.0.0~172.31.255.255

Class C Address: 192.168.0.0~192.168.255.255

The first set of numbers for Class A addresses is 1~126. Note that the numbers 0 and 127 are not used as Class A addresses, the number 127 is reserved for the internal loopback function, and the number 0 indicates that the address is a local host and cannot be transmitted.

The first set of numbers for Class B addresses is 128~191.

The first set of numbers for Class C addresses is 192~223.


1. Class A Address

The Class A address is represented by: 0.0.0.0~126.255.255.255, the default netmask is: 255.0.0.0. A-class address is assigned to a particularly large network use.

Class A networks use the first set of numbers to represent the address of the network itself. The following three sets of numbers are the addresses of the hosts connected to the network.

A large network assigned to a large number of hosts (direct individual users) and a small number of local network networks. such as IBM's network.

2. Class B Address

Class B addresses are represented in the following range: 128.0.0.0~191.255.255.255. The default netmask is: 255.255.0.0. Class B addresses are assigned to normal medium-sized networks. Class B networks use the first to second set of numbers to represent the address of the network. The latter two sets of numbers represent the host addresses on the network.

3. Class C Address

Class C addresses are represented in the following range: 192.0.0.0~ 223.255.255.255, the default netmask is: 255.255.255.0;c class address assigned to a small network, such as the general LAN and Campus network, the number of hosts can be connected to the at least, using the user is divided into several segments for management. C Network Class Network address is represented by three sets of numbers. The last set of numbers as the host address on the network.

Indeed, there are still class D address e addresses. But there are two special destination addresses. Here is a simple introduction: D-so-called broadcast address Class A address. The time for a special protocol sends the information to the node that is selected.

The EA class address is reserved for future use.

IP classification Address How the--a,b,c class is divided