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IP subnetting and Variable Length Subnet masks

Subnetting Basics
Advantages of subnetting (subnetting):
1. Reduce network traffic
2. Improve network performance
3. Simplified management
4. Easy to expand geographical range
How to creat subnets
How do I divide subnets? First of all, to memorize the power of 2:2 of the 0-to-9-square values are: 1,2,4,8,16,32,64,128,256 and 512. What's more, it is necessary to understand that the Sub-network division is to take the host bit, take the part of the take-off as a sub-network. So this means dividing the subnets more, The less hosts will be
Subnet Masks
The subnet mask is used to identify which part of the IP address is the network address, which part is the host address, which consists of 1 and 0, a length of 32 bits, and a total of 1 bits representing the network number. Not all networks require subnets, so there are 1 concepts: The default subnet mask (defaults subnet mask). The default subnet mask for Class A IP addresses is 255.0.0.0; The Class B is 255.255.0.0; Class C for 255.255.255.0
Classless Inter-Domain Routing (CIDR)
CIDR is called non-class inter-domain routing, which is commonly used by ISPs to assign addresses to customers, and the ISP provides 1 blocks (block size) for the client, similar to this:192.168.10.32/28,This number tells you what your subnet mask is,/28 for how many bits are 1, max/32. But the 1 points you have to know are: either Class A or Class B or other class addresses, the maximum available is only 30/, that is, 2 bits are reserved for the main camera
CIDR value
1. Mask 255.0.0.0:/8 (Class A address default mask)
2. Mask 255.128.0.0:/9
3. Mask 255.192.0.0:/10
4. Mask 255.224.0.0:/11
5. Mask 255.240.0.0:/12
6. Mask 255.248.0.0:/13
7. Mask 255.252.0.0:/14
8. Mask 255.254.0.0:/15
9. Mask 255.255.0.0:/16 (class B address default mask)
10. Mask 255.255.128.0:/17
11. Mask 255.255.192.0:/18
12. Mask 255.255.224.0:/19
13. Mask 255.255.240.0:/20
14. Mask 255.255.248.0:/21
15. Mask 255.255.252.0:/22
16. Mask 255.255.254.0:/23
17. Mask 255.255.255.0:/24 (class C address default mask)
18. Mask 255.255.255.128:/25
19. Mask 255.255.255.192:/26
20. Mask 255.255.255.224:/27
21. Mask 255.255.255.240:/28
22. Mask 255.255.255.248:/29
23. Mask 255.255.255.252:/30

Variable Length Subnet Masks (VLSM)
Changing the role of the eldest son Netmask (VLSM): Saving IP address space; Reduce routing table sizeWhen using VLSM, the routing protocol used must be able to support it, including RIPV2,OSPF,EIGRP and BGP.

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