Classful IP

J-Dubs

Does anyone have a way of remembering the Class A, B, and C ranges, such as a mnemonic?

dynamik

Are you familiar with the binary form of IP addresses? It's pretty easy if you are.

A, the first bit is 0.
B, the first two bits are 10.
C, the first three bits are 110
D, the first four bits are 1110 (multicast)
E, the first four bits are 1111 (reserved)

Therefore,
The first octet range of A is: 00000000 - 011111111 (0-127)
The first octet range of B is: 10000000 - 101111111 (128-191)
The first octet range of C is: 11000000 - 110111111 (192-223)
The first octet range of D is: 11100000 - 110111111 (224-239)
The first octet range of E is: 11110000 - 111111111 (240-256)

You'll just have to memorize the reserved networks:
"Zero" Addresses: 0.0.0.0-0.255.255.255
Loopback: 127.0.0.0-127.255.255.255
APIPA: 169.254.0.0-169.254.0.0
Private A: 10.0.0.0 - 10.255.255.255
Private B: 172.16.0.0 - 172.31.255.255
Private C: 192.168.0.0 - 192.168.255.255

Wikipedia has a few others I wasn't familiar with. I wouldn't worry about them for what you're doing here.

http://en.wikipedia.org/wiki/Classful_network

gojericho0

No easy memory techniques, but if you can do binary math that is the easiest way to figure it out when you forget:

000 = Class A 1 - 126 (127 used for loopback)
100 = Class B 128 - 191
110 = Class C 192 - 223
111 = Class D Used for Multicast

J-Dubs

Well, here's my memory technique:

Class A has a range of 128 (0-127)
Class B has a range of 64 (128-191)
Class C has a range of 32 (192-223)

Group that with what dynamik said and it should be all good

0
10
110