Comparing manual and automatic methods for populating routing tables.
A router's routing table can be populated in two ways: statically or dynamically. Static routing involves a network administrator manually configuring routes into the routing table. The administrator explicitly defines the path a packet must take to reach a specific destination network. This approach is straightforward, secure (as the paths are fixed and predictable), and uses no router CPU cycles or network bandwidth to exchange routing information. However, static routing has significant drawbacks. It is not scalable; manually configuring routes for a large, complex network is extremely time-consuming and prone to errors. Most importantly, it is not fault-tolerant. If a link on a statically defined path goes down, the router has no way to automatically find an alternate path. The administrator must manually intervene to reconfigure the routes. Because of these limitations, static routing is typically only used in very small networks or for specific purposes, like defining a default route (a 'gateway of last resort'). Dynamic routing is the more common and powerful approach. In dynamic routing, routers use a special routing protocol to automatically learn about available networks and calculate the best paths. They exchange routing information with each other and can dynamically adapt to changes in the network topology. If a link fails, the routers will automatically detect the change, update their information, and reroute traffic around the failure. This makes the network scalable and resilient. Examples of dynamic routing protocols include RIP, OSPF, EIGRP, and BGP.