Subnetting simply means dividing network into two more network in other to reduced network traffic, optimized network performance and for simplified network managment.

CIDR means Classless Inter-Domain Routing ; it is basically the method that ISP use to allocate an amount of addresses to a company. When you receive a block addresses from an ISP, what you get will look like this 192.168.10.32/28. what this is telling you is what your subnet mask is. the slash notation(/) means how many bits are turned on(1s)

I will break subnetting in class A , B, C for people that want to write CCNA

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