because of the peer timing out, traffic disruption occurs from that point onwards, even if the systemcontinues to maintain valid routing information in the hardware and is capable of forwarding traffic.LACP and IPv6 RoutingThe following IPv6-related actions are performed during the reload phase:• The system saves all the dynamic ND cache entries to a database on the flash card. After the systemcomes back online, and the Dell Networking OS image is loaded and the corresponding softwareapplications on the system are also activated, the following processes specific to IPv6 are performed:• If a database of dynamic ND entries is present on the flash, the information is read and the ND entriesare restored (to the IPv6 subsystem as well as the kernel); the entries are installed on the switch asquickly as possible. At the same time, the entries are changed to an initial (“incomplete”) state so thatthey are refreshed (and flushed, if not learnt again). The database on the flash is also deletedimmediately.• To ensure that the adjacent systems do not time out and purge their ND cache entries, the age-outtime or the reachable time for ND cache entries must be configured to be as high as necessary. Dellrecommends that you configure the reachable timer to be 90 seconds or longer.BGP Graceful RestartWhen the system contains one or more BGP peerings configured for BGP graceful restart, fast bootperforms the following actions:• A closure of the TCP sessions is performed on all sockets corresponding to BGP sessions on whichGraceful Restart has been negotiated. This behavior is to force the peer to perform the helper role sothat any routes advertised by the restarting system are retained and the peering session will not godown due to BGP Hold timeout.• Termination of TCP connections is not initiated on BGP sessions without GR because such a closuremight cause the peer to immediately purge routes learnt from the restarting system.• When BGP is started, it sets the R-bit and F-bit in the GR capability when bringing up the session withpeers for which BGP GR has been configured. This is the standard behavior of a restarting system andensures that the peer continues to retain the routes previously advertised by the system.• The system delays sending the BGP End-of-RIB notification to peers with whom BGP GR has beennegotiated to ensure that the local routes of the system are advertised to the peers, if required by theconfiguration.• If BGP GR is enabled on any peering session, the timeout values used for the BGP hold timer do nottake effect.Cold Boot Caused by Power Cycling the SystemWhen you perform a power-cycle operation on a system that is configured with the optimized bootingfunctionality, the system goes through its regular boot sequence even if it is configured for fast boot.When the system comes up, it is expected that there will be no dynamic ARP or ND database to restore.The system boot up mode will not be fast boot andUnexpected Reload of the SystemWhen an unexpected or unplanned reload occurs, such as a reset caused by the software, the systemperforms the regular boot sequence even if it is configured for fast boot. When the system comes up,Flex Hash and Optimized Boot-Up 333
