4.2 Configuring RIP v2  
  4.2.3 Discontiguous subnets and classless routing  
Route summarization reduces the amount of routing information in the routing tables. RIP v1 always uses automatic summarization. The default behavior of RIP v2 is to summarize at network boundaries the same as RIP v1. Use the no auto-summary command with the RIP process to turn off summarization and allow subnets to be advertised across network boundaries. This allows RIP v2 to perform routing between discontiguous subnets by advertising subnet information.

Router(config)#router rip
Router(config-router)#version 2
Router(config-router)#no auto-summary