What are difference between classful and classless IP addressing?

Classful Addressing:-

1) In Classful addressing it divides IP address into network ID and host ID

for example Class A :- has first octet as network ID and last three octet as Host ID

Class B :- has first two as network ID and last three two as Host ID

Class C :- has first three as network ID and last  octet as Host ID

2) Here class A,B and C are used where as class D is used for multicasting and class D for research

3) Disadvantage is that it limit the number of network that can be provided to the network

4) Example RIP(Routing Information Protocol) protocol uses classful addressing

5) Class A  :\8 as (1 octet is network ID) , Class B :-\16 , Class C : \24

6) Same Subnet mask is used in complete network

Classless Addressing :-

1) It allows us to use variable length subnet mask so also known as VLSM (Variable Length Subnet Mask)

2) Different subnet mask used in same network.

3) In this there is no boundary on host id and network id

4) Classless Addressing also known as CIDR(classless interdomain routing)

5) There is no default subnet mask in classless routing.