IPv4 Address Calculation for beginners

Internet Protocol version 4 (IPv4)

• 32 bit address
  • Example : 11000000 10101000 01100100 00000001
• Divided into 4 groups
• So each group contains 8 bits.
• To separate groups we use PERIODS
  • Example : 11000000 . 10101000 . 01100100 . 00000001
• The format of IP address is dotted decimals
  • We have to convert those binary bits in numbers (decimals).
  • Example : 192 . 168 . 100 . 1

Starting number of each group must be 00000000 (0)
Ending number of each group must be 11111111 (255).

Classes of IP Address

How to Find Class of an IP Address?

Class	Range	Size	Hosts
A	1 – 126	Large	16,777,214
B	128 – 191	Medium	65,534
C	192 – 223	Small	254
D	224 – 239	Reserved
E	240 – 254	Reserved

The Class D IP address is reserved for Multicast.

The IP address starting 0, 127, 255 are also reserved. The IP address starting with 127 is reserved for loopback address.

Parts of IP Address

The IP address does contain 2 parts. One is Network Part and another is Host Part.



But Network part and Host part will be vary with each class.



Class A has 8 bits of Network Part and 24 bits of Host Part.
Class B has 16 bits of Network Part and 16 bits of Host Part.
Class C has 24 bits of Network Part and 8 bits of Host Part.

When a design a network, The Network part of all IP address must be command and host part must be unique.

What is Subnet Mask?

Subnet Mask is used by networking devices to find out the network and host bits of IP address.
The Subnet Mask is contiguous. First Network bits and then Host bits.
For Subnet Mask: Network bits are 1’s and Host bits are 0’s

Example:

 

Number of hosts:

We have a formula to find out the number of hosts in each class. And the formula is  2ⁿ – 2.
And the value of n is  number of hosts bits.

Class A	224 – 2	16,777,214
Class B	216 – 2	65,534
Class C	28 – 2	254

Reserved Address is Every Network.

In Every Network there are 2 address are reserved and that’s why we minus 2 from finding number of host addresses. One is used for Routing and we call it as Network Address and another one is used for local broadcast and we call it as Broadcast Address.

For Network Address, the network part are same as the network part IP address but the host bits of IP were 0.

For Broadcast Address, the network part are same as the network part IP address but the host bits of IP were 1.



Exercise 1

In this exercise we can find out subnet mask, network broadcast address, valid ip range of the network, and number of host on the network of Class C IP address.

IP Address – 192.168.100.14

The Above IP address belong to Class C.

Then the subnet mask is 255.255.255.0.

Ok. The first 3 groups of this IP address (not subnet mask) is host bits and the last group is host part.

Then Network Address must be : 192.168.100.0
Because all bits in the last group were 0’s : 192.168.100. 00000000
The Broadcast Address must be : 192.168.100.255
Because all bits in the last group were 1’s : 192.168.100. 11111111

The Network IP range must be from 192.168.100.1 to 192.168.100.254

Number of Host : 2⁸ – 2 = 254.

Exercise 2

In this second exercise we can find out subnet mask, network broadcast address, valid ip range of the network, and number of host on the network of class B address.

IP Address – 172.16.100.55

The Above IP address belong to Class B.

Then the subnet mask is 255.255.0.0.

Ok. The first 3 groups of this IP address (not subnet mask) is host bits and the last group is host part.

Then Network Address must be : 172.16.0.0
Because all bits in the last group were 0’s : 172.16. 00000000 . 00000000
The Broadcast Address must be : 172.16.255.255
Because all bits in the last group were 1’s : 172.16. 11111111 . 11111111

The Network IP range must be from 172.16.0.1 to 172.16.255.254

Number of Host : 2¹⁶ – 2 = 65534.

Exercise 2

In this second exercise we can find out subnet mask, network broadcast address, valid ip range of the network, and number of host on the network of class A address.

IP Address – 10.56.42.5

The Above IP address belong to Class A.

Then the subnet mask is 255.0.0.0.

Ok. The first 3 groups of this IP address (not subnet mask) is host bits and the last group is host part.

Then Network Address must be : 10.0.0.0
Because all bits in the last group were 0’s : 10. 00000000 . 00000000 . 00000000
The Broadcast Address must be : 10.255.255.255
Because all bits in the last group were 1’s : 10. 11111111 . 11111111 . 11111111

The Network IP range must be from 10.0.0.1 to 10.255.255.254

Number of Host : 2⁸ – 2 = 16,777,254.

The End