EIGRP Graceful Restart
EIGRP graceful restart introduces support for non stop forwarding. The basis of this idea is : there is a device with two route processors and multi layer switching. There are other devices, its neighbors that can act as helpers, also called NSF aware. When routing sessions are setup the two parts negotiate graceful restart capabilities: NSF capable can be helped by NSF neighbors during a route processor switchover: the NSF capable device has to switchover it advices its neigbors of this. the neighbors don't react to missing hello packets (switchover can take time to complete) by tearing down the sessions and keep sending traffic to NSF capable device. During switchover the linecards use CEF tables to forward traffic. If no topolo...
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