Holddown timer

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The holddown timer is an algorithm that is supposed to ensure the stability of routed computer networks .

If several network topologies are connected to one another, routers are required at the branch offices , which should determine the fastest or best path for a data packet through the network. In order to be able to carry out this process efficiently, routers save the topology of the network locally in a routing table .

If a network fails, it is not immediately deleted from the table, but is left there for a certain time (the “hold-down time”), but is marked as “not reachable”. This enables other routers to adjust to it and the network to return to a stable state. In addition, the creation of routing loops is prevented, because during the holddown time the router does not accept a route with a higher metric than the route previously marked as inaccessible. Each route is only accepted by the router, which informed about the failed route, since the failed route could be available again or an alternative route was found.

Web links

  • RFC 2091 , "Triggered Extensions to RIP to Support Demand Circuits"