Description of IP A/B/C/D/E address class, network ID, and host ID
An IPv4 network address consists of 4 bytes, generally 4 decimal digits, each digit from 0 to 255, separated by periods.
Network address: put it in front to indicate which network this IP address belongs to on the Internet;
• Host Address: Placed on the back to indicate which device this IP address belongs to in a given network.
The network ID and the host ID have a master-slave relationship.
IP addresses can be divided to 5 categories A. B. C .D .E
class A
Description of the IP address in binary, decimal, and hexadecimal numbers
Description of IP A/B/C/D/E address class, network ID, and host ID
Class A IP address means: in the four segment number of the IP address (eg: byte1. byte2. byte3. byte4), the first segment number (byte1) is the network number, and the remaining three number segments (byte2. byte 3. bytes 4) are the numbers of the local computer.
If the IP address is represented in binary, then the Class A IP address consists of a 1-byte network address and a 3-byte host address, and the highest part of the network address must be "0".
Class A IP address range: 1.0.0.0 ~ 127.255.255.255, available IP address range: 1.0.0.1 ~ 127.255.255.254.
The network identifier in a Class A IP address is 7 bits long, and the host identifier is 24 bits long. The number of Class A network addresses is small (2 ^ 7 - 2 = 126), and it can be used to accommodate more than 16 million computers in large networks (2 ^ 24 - 2 = 16,777,214).
(Default subnet mask: 255.0.0.0 or 0xFF000000). Generally used for large networks.
class B
Description of the IP address in binary, decimal, and hexadecimal numbers
Description of IP A/B/C/D/E address class, network ID, and host ID
Class B IP address means: in the number of four segments of the IP address (eg: byte1. byte2. byte3. byte4), the first two segments of the number (byte1.byte2) is the network number, and the last two digits (byte3 4) bytes are two numbers of the local computer.
If an IP address is represented in binary, then a Class B IP address consists of a two-byte network address and a two-byte host address. The highest bit in the network address must be "10".
Class B IP address range: 128.0.0.0 ~ 191.255.255.255, available IP address range: 128.0.0.1 ~ 191.255.255.254.
Class B IP addresses contain a (14 bit) network identifier and a0( 16 bit) host identifier. Class B network addresses are suitable for medium-sized networks (2^14 = 16384), and each network can accommodate more than 60,000 computers (2^16-2 = 65534).
(Default subnet mask: 255.255.0.0 or 0xFFFF0000). Usually used for medium sized networks.
class C
Description of the IP address in binary, decimal, and hexadecimal numbers
Description of IP A/B/C/D/E address class, network ID, and host ID
Class C IP address means: in the four segment number of the IP address (eg: byte 1. byte 2. byte 3. byte 4), the first three-part number (byte 1. byte 2. byte 3) is the network number, The remaining number (byte 4) is the local computer number.
If an IP address is represented in binary, then a Class C IP address consists of a 3-byte network address and a 1-byte host address. The highest bit in the network address must be "110".
Class C IP address range starts with / 192.0.0.0 ~ 223.255.255.255 , available IP address range starts : 192.0.0.1 - and ends with 223.255.255.254 .
The network identifier in a Class C IP address is 21 bits long, and the host identifier is 8 bits long. The number of Class C network addresses is large (2^21=2097152), which is suitable for small-scale local area networks. Each network can only contain up to 254 computers (2^8 - 2 = 254).
(Default subnet mask: 255.255.255.0 or 0xFFFFFF00). Generally used for small networks.
class D
Description of the IP address in binary, decimal, and hexadecimal numbers
Description of IP A/B/C/D/E address class, network ID, and host ID
We notice The first four bits of the Class D address are always like this 1 1 1 0 . Presetting the first 3 bits to 1 means that the Class D address starts at 128 + 64 + 32 = 224. The fourth bit is 0, which means that the maximum value of the Class D address is 128 + 64 + 32 + 8 + 4 + 2 + 1 = 239.
Class D IP address range: 224.0.0.0 ~ 239.255.255.255.
Class D IPv4 addresses do not working between network addresses and host addresses.
Class D IP addresses are reserved for use by the Internet Architecture Board (IAB) for multicast addresses (one-to-many connection).
class E
Description of the IP address in binary, decimal, and hexadecimal numbers
Description of IP A/B/C/D/E address class, network ID, and host ID
The first 4 bits of a Class E IP address are always 1111. Presetting the first 4 bits to 1 means that the Class E address starts at 128 + 64 + 32 + 16 = 240.
Class E IP address range: 240.0.0.0 ~ 247.255.255.255.
Class E IPv4 addresses do not working between network addresses and host addresses.
Class E IP addresses are reserved for future use, usually for research purposes. Therefore, there are no Class E addresses available on the Internet.
As you can see, there is no overlap between the different types of IP address fragments. The five classes of IP addresses also differ in terms of use:
• Class A IP addresses are used by government working .
• Class B IP addresses are allocated to medium-sized companies;
• Class C IP addresses can be Totally customized .
• Class D IP addresses are used for multicasting .
• Class E IP addresses are reserved for experiments scientific and research .
The current popular IPv4 classification is based on different group of network numbers and host numbers or id . For 32-bit addresses, the occupied lengths of the class A, B, and C network numbers are 8, 16, and 24, respectively, and the class D address is used for multicasting. Class E title pieces.
All network space calculations must be "subtracted by 2" because two reserved addresses are subtracted: "0" for this network and "255" for broadcast.
Some private IP addresses:
0.0.0.0 can not be pinged. In the server, 0.0.0.0 is not a real IP address, it represents all IPV4 addresses in the device. The port that listens on 0.0.0.0 is the port that listens on all IP addresses in the device.
127.0.0.1 is a reserved address, generally used for the loopback address, which is equivalent to localhost or local IP address.
255.255.255.255 is used to represent the broadcast address of the local network. It cannot be forwarded or bypassing through the gateway . but will be sent to all hosts on the same network (segment) , so it is also called (broadcast) by many people.
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