Back ] Next ]

Forms of IP Addressing

Once upon a time...

When the internet was just starting out, it was thought that order is needed.

IP addresses were classified into 5 categories or Classes. As such, there are five forms of IP addresses:

 

 

 

Class & description

Address Range

Remarks

Class A :

126 networks, each can have up to (16M-2) nodes.

(1.0.0.0 - 127.255.255.255)

Huge networks

Class B:

(16K-2) networks, each can have up to (64K-2) nodes

(128.0.0.0 - 191.255.255.255)

Quite Large networks

Class C:

(2M-2) networks, each can have up to 254 nodes.

(192.0.0.0 - 223.255.255.255)

Medium & Small networks

Class D:

a multicast address.

(224.0.0.0 - 239.255.255.255)

multicast is sending the same content to many users at once (like watching TV)

Class E:

 

 

reserved for future use.

(240.0.0.0 - 247.255.255.255)

 

Remarks:   1) By convention we don't use series of 0 or of 1 as legal address !!
                  2) By convention we save the address 127.0.0.0 for loopback.
                  3) The address 0.0.0.0 is used to represent a default route.

                 4) The maximum number of nodes on each net is (2^n)-2 when n is number of bits for host ID.