|  | 11.4 | Link-State Routing
| 11.4.3 | How topology changes propagate through the network of routers
Link-state algorithms rely on using the same link-state updates. Whenever a link-state topology changes, the routers that first become aware of the change send information to other routers or to a designated router that all other routers can use for updates. This involves sending common routing information to all routers in the internetwork. To achieve convergence, each router does the following: keeps track of its neighbors: each neighbor's name, whether the neighbor is up or down, and the cost of the link to the neighbor. constructs an LSA packet that lists its neighbor router names and link costs, including new neighbors, changes in link costs, and links to neighbors that have gone down. sends out this LSA packet so that all other routers receive it. when it receives an LSA packet, records the LSA packet in its database so that it updates the most recently generated LSA packet from each router. completes a map of the internetwork by using accumulated LSA packet data and then computes routes to all other networks by using the SPF algorithm. Each time an LSA packet causes a change to the link-state database, the link-state algorithm (SPF) recalculates the best paths and updates the routing table. Then, every router takes the topology change into account as it determines the shortest path to use for packet routing.
| Web Links
| Dijkstra's algorithm