Easy Way To Remembering Class C Subnetting

What do we should know about class C subnetting (CIDR)? Remembering this will make you easy to solve your problem on exam even on your work. I think you don't need to count everytime you need, just placed this into your mind.

/25 What do we know about a /25?
128 mask
1 bit on and 7 bits off (10000000)
Block size of 128
Subnets 0 and 128
2 subnets, each with 126 hosts

/26 What do we know about a /26?
192 mask
2 bits on and 6 bits off (11000000)
Block size of 64
Subnets 0, 64, 128, 192
4 subnets, each with 62 hosts

/27 What do we know about a /27?
224 mask
3 bits on and 5 bits off (11100000)
Block size of 32
Subnets 0, 32, 64, 96, 128, 160, 192, 224
8 subnets, each with 30 hosts

/28 What do we know about a /28?
240 mask
4 bits on and 4 bits off
Block size of 16
Subnets 0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224, 240
16 subnets, each with 14 hosts

/29 What do we know about a /29?
248 mask
5 bits on and 3 bits off
Block size of 8
Subnets 0, 8, 16, 24, 32, 40, 48, etc.
32 subnets, each with 6 hosts

/30 What do we know about a /30?
252 mask
6 bits on and 2 bits off
Block size of 4
Subnets 0, 4, 8, 12, 16, 20, 24, etc.
64 subnets, each with 2 hosts

Easy, right?
Just need time to placed it all into your mind. Print it out and paste on your wall where everytime you can see it.
Happy!