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

Continue reading “Advanced Cisco BGP features: NSF”

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Advanced Cisco BGP features: BFD

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

topo-2routers-dual-link

Bidirectional Forwarding Detection for BGP

I have just one note here. BFD can’t be enabled simultaneously with NSF for BGP. Even for other protocols, extreme care should be taken while implementing BFD with NSF. Depending on the platform, there may be enough of a traffic outage during the switchover to cause BFD to prematurely signal a link failure. When BFD is running on the RP, some platforms are not able to detect a switchover before the BFD protocol times out; these platforms are referred to as slow switchover platforms. Continue reading “Advanced Cisco BGP features: BFD”

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