Networking CIDR explained

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Networking CIDR explained.md

The table at the bottom of this gist was copied from: http://software77.net/cidr-101.html

10.0.0.0 is a 32 bit number split into four 8 bit groups (8, 16, 24, 32)

Note: 1 byte == 8 bits (so 10 representing a single byte)

Where n (below) is given the value 8, 16, 24, or 32

10.0.0.0/n

8 states the first 8 bits is accounted for (by the 10 we’ve specified).
Meaning the rest can be added up to their max of 255 (10.255.255.255)

16 states the first 16 bits is accounted for (by the 10.0 we’ve specified).
Meaning the rest can be added up to their max of 255 (10.0.255.255)

24 states the first 24 bits is accounted for (by the 10.0.0 we’ve specified).
Meaning the rest can be added up to their max of 255 (10.0.0.255)

32 states the first 32 bits is accounted for (by the 10.0.0.0 we’ve specified).
Meaning the rest can be added up to their max of 255 (10.0.0.0)

Example: 10.0.0.1

IP	10								0								0								1
8 Bit Blocks	8 bits [24-31]								8 bits [16-23]								8 bits [08-15]								8 bits [00-07]
Bit #	31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00
Decimal	128	64	32	16	8	4	2	1	128	64	32	16	8	4	2	1	128	64	32	16	8	4	2	1	128	64	32	16	8	4	2	1
Binary	0	0	0	0	1	0	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	1

Notice the binary row marks 1 for the decimal numbers that add up to the specified byte
e.g. if you want 254 then you have 1 in all of the binary columns (under decimal) except the 1 at the end