Every server needs an IP address to communicate with another server.

An IP address is needed whether the communication is:

• Internal
• Public / Internet level

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An IP address is made up of four octets.

Example:

10.0.0.0

Each octet contains 8 bits.

┌─────────┬─────────┬─────────┬─────────┐
│ Octet 1 │ Octet 2 │ Octet 3 │ Octet 4 │
│  8 bits │  8 bits │  8 bits │  8 bits │
└─────────┴─────────┴─────────┴─────────┘

Each octet can contain a combination of binary numbers.

Each value is obtained by multiplying the previous value by 2:

1 × 2 = 2
2 × 2 = 4
4 × 2 = 8
8 × 2 = 16
16 × 2 = 32
32 × 2 = 64
64 × 2 = 128

Therefore, one octet can use the following binary place values:

2⁷   2⁶   2⁵   2⁴   2³   2²   2¹   2⁰
128   64   32   16    8    4    2    1

There are 8 digits/bits in one octet.

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An IP address can be represented using binary numbers.

For example:

0 0 0 0 0 0 0 0

The corresponding place values are:

2⁷  2⁶  2⁵  2⁴  2³  2²  2¹  2⁰

When a bit is changed from 0 to 1, its corresponding value is added.

For example:

00000001

means:

1 = 2⁰

Similarly:

00000010

means:

2 = 2¹

And:

00000011

means:

2 + 1 = 3

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If the IP starts from:

0.0.0.0

the IP addresses increase sequentially:

0.0.0.0
0.0.0.1
0.0.0.2
0.0.0.3
...
0.0.0.255

After reaching 255 in the last octet, the next IP becomes:

0.0.1.0

Then:

0.0.1.1
0.0.1.2
...
0.0.1.255

The calculation therefore moves to the next octet after the previous octet reaches its limit.

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Subnet masking determines which octets are fixed and which octets can be changed.

10.0.0.18

Here, we mask/fix the first octet:

[10].0.0.18

The first octet is fixed.

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10.0.0.16

Here, we mask/fix the first and second octets:

[10.0].0.16

The first two octets are fixed.

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10.0.0.24

Here, we mask/fix the first three octets:

[10.0.0].24

The first three octets are fixed.

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For every condition, the unfrozen octets can be edited.

For example:

[10].0.0.18

Only the first octet is fixed, while the remaining octets can be changed.

Similarly:

[10.0].0.16

The first two octets are fixed.

And:

[10.0.0].24

The first three octets are fixed.

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• An IP address consists of four octets.
• Each octet contains 8 bits.
• Each bit represents a power of 2.
• The powers of 2 from 2⁰ to 2⁷ are used to calculate the value of an octet.
• IP addresses increase sequentially.
• When the last octet reaches 255, the next octet increases.
• Subnet masking fixes specific octets.
• The unfrozen octets can be edited according to the subnet condition.