Various network addresses

There are millions of hosts on the Internet. to distinguish these hosts, people assign a special "Address" to each host as the identifier, called an IP address, it is like your online ID card, to view your IP address, click Start> run in the Windows 9x system. Then, enter winipcfg (2000/XP, and enter ipconfig). Then, press Enter. IP is the abbreviation of Internet protocol. To transfer information between hosts, you must know the IP address of the other host. The length of each IP address is 32 bits, which are divided into 4 segments. Each segment has 8 bits (1 byte). It is usually expressed in decimal format. The value range of each segment is 1 ~ 254. segments and segments are separated by decimal points. Each byte (segment) can also be expressed in hexadecimal or binary format. Each IP address consists of two IDs (ID code): The network ID and the host ID. All hosts on the same physical network use the same network ID. A host on the network (such as workstation, server, and router) corresponds to a host ID. In this way, the four bytes of the IP address are divided into two parts. One part is used to indicate the specific network segment, that is, the network ID, and the other part is used to indicate the specific node, that is, the host machine ID. These 32-bit addresses are divided into five categories, which correspond to Class A, Class B, Class C, Class D, and Class E IP addresses respectively.
1. Class a ip Address

A Class a ip address consists of a 1-byte network address (each byte is 8 bits) and a 3-byte host address. The highest bit of the network address must be "0 ", that is, the range of the first digit is 1 ~ 127. Each class A address can be connected to 16387064 hosts, and the Internet has 126 Class A addresses.

2. Class B IP Address

A B-type IP address consists of two bytes of network address and two bytes of host address. The maximum bit of network address must be "10", that is, the range of the first digit is 128 ~ 191. Each class B address can connect 64516 hosts, and the Internet has 16256 Class B addresses.

3. Class c ip Address

A Class C address is composed of three bytes of network address and one byte of host address. The highest bit of network address must be "ll0", that is, the first digit range is 192 ~ 223. Each class C address can connect 254 hosts, and the Internet has 2054512 Class C addresses.

4. Class D addresses are used for Multi-Point broadcasting.

The first byte starts with "lll0" and the number range of the first byte is 224 ~ 239 is a multi-point broadcast address, used for the transmission of multi-destination information, and as a backup. The full zero ("0.0.0.0") Address corresponds to the current host. The full "1" IP address ("255.255.255.255") is the broadcast address of the current subnet.

5. Class E address

Starting from "llll0", that is, the range of the first digit is 240 ~ 254. Class E address is retained for experiment and development only.

Several IP addresses used for special purposes

① All IP addresses with host segments (I .e. host machines) IDs set to "0" are called network addresses. For example, 129.45.0.0 is a Class B network address.

② The IP address with the host ID set to "1" (that is, 255) is called a broadcast address. For example, 129.45.20.255 is a broadcast address of type B.

③ The network ID cannot start with "127" in decimal format. The number 127 in the address is reserved for diagnosis. For example, 127.1.1.1 is used for loop testing. At the same time, the first eight-bit Group of the network ID cannot be set to "0", and "0" indicates the local network. IP addresses with all network IDs of "0" and "1" are retained.

Internet designers do not know how it will develop. Some people imagine that an Internet may contain several networks with many hosts. Others predict that there are many networks and there are not many hosts on each network. As a compromise, Internet addresses are suitable for large networks and small networks. They are identified as 32-bit, but there are three types. The IP address is customized, and its highest bit defines the type of the IP address. Class A addresses support multiple hosts in one network: the highest bit is 0, followed by a 7bit Network part and a 24bii host part. In Class B address, the highest bit is non-0, followed by the 14bit network number and 16bii host number. The Class C address starts with 110 and follows the 2lbit network number and 8bit host number. Generally, the Internet address is given by some characters. An address is composed of four parts in decimal format and separated by vertices. For example, 10.0, 0.51, and 128.10.2.1 are Internet addresses of Class A and Class B respectively.