IP address classification, which determines whether a network segment is a subnet supernetwork

One 、IP Address classification

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Two 、IP Address range

A class IP Address

One A class IP Address by 1 Byte network address and 3 Byte host address composition , The highest bit of the network address must be “0”.

The highest bit of the network address is 0 The address of , by A Class address . The Internet ID yes 0 Out-of-service ,127 As a reserved network segment , therefore A Class address 1 Part of the value range 1-126.

A The default subnet mask of class network is 255.0.0.0. host ID From the first 2 part 、 The first 3 Section and section 4 Part of it is made up of , The value range of each part 0-255, common 256 Species value , One A The number of class network hosts is 256×256×256=166777216, Here you need to subtract 2, host ID whole 0 The address of is the network address , And the mainframe ID All for 1 The address of is the broadcast address .

Address range 1.0.0.1-126.255.255.254

Binary representation as ：00000001 00000000 00000000 00000001 - 01111110 11111111 11111111 11111110

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B class IP Address

One B class IP Address by 2 Byte network address and 2 Byte host address composition , The highest bit of the network address must be “10”.

The highest bit of the network address is 10 The address for B Class address .IP Address No 1 The value range of part is 128-191.

B The default subnet mask of class network is 255.255.0.0. host ID From the first 3 Section and section 4 Part of it is made up of , Every B The maximum number of hosts that a class network can accommodate 256×256-2=65023.

Address range 128.1.0.1-191.255.255.254

Binary representation as ：10000000 00000001 00000000 00000001 - 10111111 11111111 11111111 11111110

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C class IP Address

One C class IP Address by 3 Byte network address and 1 Byte host address composition , The highest bit of the network address must be “110”.

The highest bit of the network address is 110 The address for C Class address .IP Address No 1 The value range of part is 192-223.

C The default subnet mask of class network is 255.255.255.0. host ID From the first 4 Part of it is made up of , Every C The maximum number of hosts that a class network can accommodate 256-2=254.

Range 192.0.1.1-223.255.255.254

Binary representation as : 11000000 00000000 00000001 00000001 - 11011111 11111111 11111110 11111110

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D class 、E class IP Address

D class IP The first byte of the address is “1110” Start , It's a reserved address .

It doesn't point to a specific network , At present, this kind of address is used in multicast （Multicast） in .

The highest bit of the network address is 1110 The address for D Class address .D Class address 1 The value range of part is 224-239. For multicast （ Also known as multicast ） The address of , The multicast address has no subnet mask .

A multicast address is used to address a group of computers at a time

Address range 224.0.0.1-239.255.255.254

With “1111” Start , Reserved for future use

E Class address reservation , For experiment and development only

The highest bit of the network address is 11110 The address for E Class address . Part I value range 240-254, Reserved for future use .

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3、 ... and 、IP Schematic diagram of address classification

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Four 、 Judge whether a network segment is a subnet or a supernetwork

Merge multiple network segments by shifting the subnet mask to the left , Moving the subnet mask to the right divides a network segment into multiple subnets , bring IP The address breaks the traditional A class 、B class 、C Class boundaries .

Determine whether a network segment is a subnet or a Supernet , It depends on whether the network segment is A Class network 、 still B Class network 、 still C Class network , Default A Class subnet mask /8,B The class subnet mask is /16,C The class subnet mask is /24.

If the subnet mask of this network segment is longer than the default subnet mask , It's a subnet , If the subnet mask of this network segment is shorter than the default subnet mask , It's super net .

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Example ：

12.3.0.0/16 This is a A Class network or C What about class network ？ Is it a Supernet or a subnet ？

answer ：IP The first part of the address is 12, This is a A Class network ,A The default subnet mask of the class address is /8, The subnet mask of this network is /16, Longer than the default subnet mask , So this is A A subnet of a class network .

namely ,A The default subnet mask of the class address is 8, therefore 12.3.0.0 The default original network segment of is 12.0.0.0/8,12 It's the network part , Next is the host . 12.3.0.0/16,12.3 It's the network segment , Next is the host . therefore 12.3.0.0/16 yes 12.0.0.0/8 A sub network subdivided .