IP Classless

Router(config)#ip classless	Instructs IOS to forward packets destined for an unknown subnet to the best supernet route
Router(config)#no ip classless	Turns off the ip classless command

Note:

A supernet route is a route that covers a range of subnets with a single entry.

Note:

The ip classless command is enabled by default in Cisco IOS Software Release 11.3 and later.