The underlying difference between dynamic and static routing is that static routing is installed manually, while dynamic routing is supported by software applications. This results in differing adaptability and as a consequence different uses.
Static routing uses a configuration file, which is loaded when the router is started up. Because it is manually configured, it cannot change after installation unless a person changes it. This means that in the event of a failure of the external network, the router must be manually updated. Because of this, static routing is best used where there are fewer than five devices and the routes are known to be stable.
Dynamic routers are suitable for use in networks where there are multiple routers. Dynamic routing, since it depends on software applications, can adapt and learn network destinations both on its own and from other routers on the network that are using the same routing protocol. As such, dynamic routers can dynamically adapt to changes in the network as well as any external network failures.
Modern networks typically use a combination of both types of routing, with a preference for dynamic routing because of its flexibility. Static routing is however more secure and does not include any advertising.