Definition Classful Address
Addresses have three parts: network; subnet; and host.
Definition Classful Routing protocols
Routing protocol does not advertise masks nor support VLSM; RIP-1 and IGRP
Definition Classful Routing (forwarding)
IP forwarding process is restricted in how it uses the default route
Definition Classless Addresses
Addresses have two parts: subnet or prefix and host
Definition Classless Routing protocols
Routing protocol does advertise masks and supports VLSM; RIP-2; EIGRP; OSPF
Definition Classless Routing (forward)
IP forwarding process has no restrictions on using the default route