8.4 The Network Layer
8.4.6 The difference between static and dynamic routing
There are two major types of routing processes, static and dynamic. Static routing is programmed by the network administrator to determine which path a packet must take to reach its destination. The administrator must maintain (including any kind of changes, additions or deletions) the routes of each network routing device. Static paths are not flexible with changing network environments. Once the static routes are programmed, the determined paths for packets do not change, regardless of changing network conditions. Static routes are most often used for security reasons.

Dynamic routing allows the router to select which path a packet must take in order to reach its destination. In doing so, a router uses routing protocols such as Routing Information Protocol (RIP), IGRP, EIGRP, or Open Shortest Path First (OSPF) to communicate with other routers to determine which path is the fastest way to transport data across an internetwork (a network of networks). Using the routing protocols, routers "talk" to each other to update what paths are best to send data through, especially while network conditions are constantly changing. Without routing or its protocols, large networks, such as the Internet, would be impossible to maintain.