Link-state routing protocols collect routing information from all other routers in the
network or within a de?¬?ned area of the internetwork. After all the information is collected, each
router, independently of the other routers, calculates its best paths to all destinations in the
network. Because each router maintains its own view of the network, it is less likely to propagate
incorrect information provided by any one particular neighboring router.
Link-state routing protocols were designed to overcome the limitations of distance vector routing
protocols. Link-state routing protocols respond quickly to network changes, send triggered
updates only when a network change has occurred, and send periodic updates (known as link-state
refreshes) at long intervals, such as every 30 minutes. A hello mechanism determines the
reachability of neighbors.
When a failure occurs in the network, such as a neighbor becomes unreachable, link-state
protocols ?¬‚ood LSAs using a special multicast address throughout an area. Each link-state router
takes a copy of the LSA, updates its link-state (topological) database, and forwards the LSA to all
neighboring devices.
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