So far we can condense what we know to:

Class A – first bit set to 0.  Address range 1-126 (127 is reserved for testing)

Network.Host.Host.Host

Class B – first bits set to 10.  Address range 128-191

Network.Network.Host.Host

Class C – first bits set to 110.  Address range 192-223

Network.Network.Network.Host

Class D – first bits set to 1110.  Address range from 224-239

Class E – first bits set to 11110.  Address range from 240-255

We only need to look at the number in the first octet to recognize which class address we are dealing with.

10.1.2.1 = Class A

190.2.3.4 = Class B

220.3.4.2 = Class C

 

 

 

 

 

 

 

 

 

 

 

 

 

Reserved Addresses

In order to help prevent wastage of IP addresses certain addresses were reserved for use on private networks. Any individual can use these addresses on their network providing they do not try to get out to the internet using them. The address allocation scheme was suggested in RFC 1918* ‘Address Allocation for Private Internets’.

IN THE REAL WORLD: In order to get out to the internet a technique known as NAT (network address translation) is used to swap your private address to a public address.

The reserved addresses are:

10.x.x.x – Any IP address beginning with 10
172.16.x.x – 172.31.x.x – Any IP starting with 172.16 to 172.31 inclusive
192.168.x.x – Any IP address starting with 192.168