Classfull routing protocol is a routing protocol that strictly. follows the classfull IP like IGRP,RIP

Classless Routing A scheme which allocates blocks of Internet addresses in a way that allows summarisation into a smaller number of routing table entries.

classful routing:in this routing only ip addresses are used..subnet mask is not used.due to which it does not support subnetting and vlsm

classless uses subnet mask alos...due to which subnetting and vlsm is possible in this case

Rip v1 is classfull routing protcol

Rip v2 is classless routing protocol

multicasting is sending data(packets) to more than one computers but not all on that network