Which statement about the BFD-BGP Multihop Client Support and cBit feature is true?
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A. B. C. D.B.
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/15-s/irg-15-s-book/irg-multihop-cbit.pdfThe BFD-BGP Multihop Client Support and cBit feature is a combination of two different technologies that are used in service provider networks to improve the convergence and response time to adjacency changes with BGP neighbors.
BFD (Bidirectional Forwarding Detection) is a protocol used to detect failures in the forwarding path between two routers. BGP (Border Gateway Protocol) is used to exchange routing information between routers in different autonomous systems. The BFD-BGP Multihop Client Support and cBit feature allows BGP to use BFD for faster detection of failures and faster convergence in the event of a link or neighbor failure.
Option A is incorrect. The BFD cBit feature does not replace BGP graceful restart or fast-failover features. These features are still used in BGP for various purposes, including reducing the impact of routing changes on the network.
Option B is partially correct. The cBit in BFD does determine if the BFD session failure is independent or dependent on the control plane. The cBit is set by the BGP speaker to indicate whether it wants BFD to use the control plane to detect failures or not.
Option C is partially correct. BFD cBit can improve BGP convergence and response time to adjacency changes by providing faster failure detection. However, the statement that the session is deactivated in the next BGP scanning interval is not entirely accurate. BFD can be configured to immediately deactivate a BGP session when a failure is detected.
Option D is incorrect. BFD cBit does not identify VPNv4 and VPNv6 prefixes in a multihomed network. Instead, BGP can be used to advertise VPNv4 and VPNv6 prefixes between different autonomous systems.
In conclusion, the correct statement is that the cBit in BFD determines if the BFD session failure is independent or dependent of the control plane, and BFD cBit can improve BGP convergence and response time to adjacency changes.