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IPs.md

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IPv4

  • 32 bits value

IP addresses can be represented in different numbering systems for different purposes, such as binary for bitwise operations, octal for simplifying calculations (add/substract), decimal for human readability, and hexadecimal for compactness.

Bits

00000000 00000001 00000010 00000100 00001000 00010000 00100000 0100000 10000000
0 1 2 4 8 16 32 64 128

Conversions

network-addressing-info-graph

Mask

Ones to the left (network part) and zeroes to the right (hosts part)

11111111000000000000000000000000

11111111111111111111111111111111 = 255.255.255.255
11111111000000000000000000000000 = 255.0.0.0
11111110000000000000000000000000 = 254.0.0.0
11111100000000000000000000000000 = 252.0.0.0
11111000000000000000000000000000 = 248.0.0.0
11110000000000000000000000000000 = 240.0.0.0
11100000000000000000000000000000 = 224.0.0.0
11000000000000000000000000000000 = 192.0.0.0
10000000000000000000000000000000 = 128.0.0.0
00000000000000000000000000000000 = 0.0.0.0

Only these decimal numbers may appear in a mask: 0, 128, 192, 224, 240, 248, 252, 254, 255

Wildcard Mask

Reverse of mask

11111111000000000000000000000000 -> 00000000111111111111111111111111

00000000000000000000000011111111 = 0.0.0.255
00000000000000000000000001111111 = 0.0.0.127
00000000000000000000000000111111 = 0.0.0.63
00000000000000000000000000011111 = 0.0.0.31
00000000000000000000000000001111 = 0.0.0.15
00000000000000000000000000000111 = 0.0.0.7
00000000000000000000000000000011 = 0.0.0.3
00000000000000000000000000000001 = 0.0.0.1
00000000000000000000000000000000 = 0.0.0.0

Only these decimal numbers may appear in a wildcard mask: 255, 127, 63, 31, 15, 7, 3, 1, 0

Prefix

Count of ones in a mask

11111111000000000000000000000000 -> 8
11111111111111110000000000000000 -> 16
11111111111111111111111100000000 -> 24

Size

How many hosts a network can contain (not including network and broadcast addresses)

(2^COUNT_OF_ZEROES_IN_MASK) -2
(2^(32 - prefix)) - 2

Network address

Any address bitwise AND mask

A B A AND B
0 0 0
0 1 0
1 0 0
1 1 1 
192.168.1.3 AND 255.255.255.0 -> 192.168.1.0

network addresses always end with 0 in binary

First host

Network address +1

192.168.1.0/24 -> 192.168.1.1

Broadcast address

Any address bitwise OR wildcard mask

A B A OR B
0 0 0
0 1 1
1 0 1
1 1 1 
192.168.1.0 OR 0.0.0.255 -> 192.168.1.255

Last host

Broadcast address -1

192.168.1.255/24 -> 192.168.1.254