|  | 11.8 | Interior Gateway Protocol (IGP) and Exterior Gateway Protocol (EGP)
| 11.8.3 | RIP
The most common method to transfer routing information between routers that are located on the same network is RIP. This Interior Gateway Protocol calculates distances to a destination. RIP allows routers that use this protocol to update their routing tables at programmable intervals, typically every thirty seconds. However, because it is constantly connecting neighboring routers, this can cause network traffic to build. RIP allows routers to determine which path it will use to send data, based on a concept known as distance-vector. Whenever data travels on a router, and thus through a new network number, it is considered to have traveled one hop. A path that has a hop count of four indicates that data traveling along that path must have passed through four routers before reaching its final destination on the network. If there are multiple paths to a destination, the router, using RIP, selects the path with the least number of hops. However, because hop count is the only routing metric used by RIP in determining best path, it is not necessarily the fastest path. Nevertheless, RIP remains very popular, and is widely implemented. This is primarily because it was one of the earliest routing protocols to be developed. Another problem with using RIP is that a destination may be located too far away for the data to reach it. With RIP, the maximum number of hops that data can travel is fifteen. Because of this, if the destination network is more than fifteen routers away, it is considered unreachable.