Some understanding of IP address classification
Recently, I have been studying Liunx, so I have read the network knowledge again. I feel that I do not understand the basic knowledge of IP classification and routing very well. I am combing these knowledge here.
IP addresses are mainly divided into A, B, C, D, E, D for multicast and E for scientific research. Class A, B and C are mainly discussed here.
The IP address is made up of 4 8bit, with a total of 2 ^ 32 possible addresses. Different types of networks are judged by the first set of 8bit.
Class An address: 0-127.* binary: 0room.*
Class B address: 128-191.* two-tier system: 10cm. *
Class C address: 192-223.* two-tier system: 110 million dollars. *
If it is assigned to users in this way, it can be seen from the concept of subnet mask that if a fixed subnet mask is assigned, the number of available host ip that each user gets is fixed and inflexible. So we use changing the subnet mask to give the AMagol BMague C network
A net
Features: fewer network addresses, that is, fewer addresses that can be assigned. But there are many host addresses, that is, a lot of IP addresses are obtained. In the future, multiple network segments can be divided by variable length subnet mask.
Subnet mask: 255.0.0.0
The number of distributable networks: 2 ^ 7-1 = 127, minus all 0. The 127th is for local loops
Number of host addresses: 2 ^ 24-2
B net
Features: there are generally many network addresses and many host addresses.
Subnet mask: 255.255.0.0
Number of distributable networks 2 ^ (6 / 8) = 65536
Number of host addresses: 2 ^ 16-2
C net
Features: there are many network addresses and few host addresses
Subnet mask: 255.255.255.0
Number of available networks 2 ^ (5 / 8 / 8) = 2 ^ 21
Number of available hosts: 2 ^ 8-2
There is also an address on each type of network that is used for private routing and cannot be used on the WAN.
Category A: 10.0.0.0 Universe 8
Category B: 172.16.0.0amp 16-172.31.0.0amp 16, which can also be denoted by 172.16.0.0amp 12
Category C; 192.168.0.0Compact 24-192.168.255.0Compact 24, or 192.168.0.0and16 table
