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JUNOS Cookbook by Aviva Garrett

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8.12. Configuring Routing Protocols to Restart Without Losing Adjacencies

Problem

You want to control when routers calculate new paths so that temporary routing-protocol failures don't cause unnecessary recalculations.

Solution

Enable graceful restart for all routing protocols on the router:

	[edit routing-options]
	aviva@RouterG# set graceful-restart

Discussion

From time to time, something happens to interrupt the operation of the routing protocols. The interruption might be a planned reinstallation of the routing software to fix a problem. The interruption might also be unplanned because a routing protocol stops running or a network link goes down but is something you might be able to respond to and repair quickly. When this happens, the routing protocols stop sending keepalive messages to their neighbors. After a short while (the actual time depends on the protocol and how it's configured), the neighbor will declare that the local router is down and, because the network topology has changed, will start calculating new paths to network destinations. This recalculation floods a lot of protocol traffic, which can disrupt the operation of the network. If you know that the downtime for the routing protocols will generally be brief, you really don't want the routing protocols to recalculate paths, only to recalculate them again once the routing protocols are back up.

Graceful restart is a way to hide the fact that a routing protocol has restarted and thus prevent path recalculations. With ...

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