Comparing static and dynamic routing

A common term used to describe dynamic routing is convergence. Convergence is the ability to work around network problems and outages — for the routing to come together despite obstacles. For example, if the main router between two end points goes down, convergence is the ability to find a way around that failed router and reach the destination. Static routing has zero convergence beyond trying the next route in its limited local routing table — if a network administrator doesn’t fix a routing problem manually, it may never be fixed, resulting in a downed network. Dynamic routing solves this problem by involving routers along the route in the decision-making about the optimal route, and using the routing tables of these routers for potential routes around the outage. In general, dynamic routing has better scalability, robustness, and convergence. However, the cost of these added benefits include more complexity and some overhead: the routing protocol uses some bandwidth for its own administration.

Comparing static and dynamic routing

Overhead                  None                                                    Varying amounts of bandwidth used for routing protocol updates

Scalability                Limited to small networks                    Very scalable, better for larger networks

Robustness              None – if a route fails it has to be fixed manually

Robust – traffic routed around failures auto- matically

Convergence           None                                                    Varies from good to excellent