CIDR stands for classless inter domain routing
there are some disdavntages with calssful addressing cidr will solve those issues
in classfull adressing if we want 100 ip adresses we can go for class c which have 256 hosts,if we want 300 ip’s we can go for class b which has more than 300 ips
cidr solve that issue by giving required number of ip addresses in block form
cidr blocks will always contains addresses in the power of 2 like 2^8,2^9…etc
There’s no classes in cidr,so how can we find network id ,host id? cidr notation will tell that,cidr notation will look like this 192.168.1.1/24,here 24 bits used for nid,remaining
bits used for host id.

subnetting in cidr

ex:20.30.40.10/25 we need 2 subnets lets find host bits host bits falls on last octet last 7 bits cause nid 25 bits convert last octet to binary

20.30.40.0 0001010
put all zeros in hid part we will get nid

20.30.40.0 0000000 to 20.30.40.0(nid)

20.30.40.0 1111111 to 20.30.40.127(last ip/brd ip)

lets do subneting

subnet1	subnet2
20.30.40.00000000	20.30.40.01000000
to	to
20.30.40.00111111	20.30.40.011111111

Range of subnet1: 20.30.40.0/26 - 20.30.40.63/26

Range of subnet2: 20.30.40.64/26 - 20.30.40.127/26

/26 beacuse one more bit used for subnetid in previous post we have seen all 1’s represent subnetid&nid

/26 also represent subnet mask Subnet Mask-1111111.1111111.1111111.11000000

vlsm in cidr 20.30.40.10/25

sunet1	subnet2	subnet3
20.30.40.00000000	20.30.40.10000000	20.30.40.11000000
to	to	to
20.30.40.01111111	20.30.40.10111111	20.30.40.11111111

Range of subnet1: 20.30.40.0 - 20.30.40.127
Range of sunet2: 20.30.40.128 - 20.30.40.192
Range of subnet3: 20.30.40.192 - 20.30.40.255