Let's get down and dirty with RIP. This protocol has three versions: RIPv1, RIPv2, and RIPng. Version 1 of this protocol is not used anymore, but you should know that RIPv1 is a class-full routing protocol, which means you need to use the same mask across your network and the same class of address. It also will not receive any updates from RIPv2 unless you specifically go into the interface and tell it to, but, again, it is not used any more. Oh, and the updates are sent as broadcast.
RIPv2 is a classless routing protocol that allows you to have different classes of addresses and different masks that would meet the needs of the network, allowing you not to waste IP addresses. This is possible due to the command no auto-summary. It does send periodic updates, but now it's using the multicast address 224.0.0.9, which is a lot easier...