Advanced Cisco BGP features: NSF

Below topology was used for this post, and all the configuration happened on two Cisco CSR1000v

topo-2routers-dual-link

BGP Nonstop Forwarding

  • During normal NSF operation, CEF on the active RP synchronizes its current FIB and adjacency databases with the FIB and adjacency databases on the standby RP
  • While switching over, the traffic is depended on CEF, once the routing protocol is converged, FIB will be updated
  • RIB repopulating happens prefix-by-prefix, thus the same for FIB and adjacency table
  • For BGP NSF, graceful-restart needs to be configured on both ends of a BGP session. Although one end could be only NSF-aware (not SSO capable)
  • BFD can’t be enabled simultaneously with NSF for BGP
  • SSO is not integrated into EIGRP, hence only NSF awareness is supported

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