300-410 · Question #58
What is a prerequisite for configuring BFD?
The correct answer is C. Cisco Express Forwarding must be enabled on all participating BFD endpoints.. Bidirectional Forwarding Detection (BFD) relies on Cisco Express Forwarding (CEF) for its rapid detection capabilities. Therefore, CEF must be enabled on all BFD-participating endpoints to ensure efficient packet forwarding for BFD control packets.
Question
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Options
- AAll routers in the path between two BFD endpoints must have BFD enabled.
- BJumbo frame support must be configured on the router that is using BFD.
- CCisco Express Forwarding must be enabled on all participating BFD endpoints.
- DTo use BFD with BGP: the timers 3 9 command must first be configured in the BGP routing process.
How the community answered
(46 responses)- A4% (2)
- B2% (1)
- C91% (42)
- D2% (1)
Why each option
Bidirectional Forwarding Detection (BFD) relies on Cisco Express Forwarding (CEF) for its rapid detection capabilities. Therefore, CEF must be enabled on all BFD-participating endpoints to ensure efficient packet forwarding for BFD control packets.
BFD is a point-to-point protocol between two direct peers; intermediate routers in the path do not need to have BFD enabled, only the endpoints of the BFD session.
Jumbo frame support is not a prerequisite for BFD operation; BFD control packets are typically small and do not require larger MTU sizes.
BFD uses small, rapidly sent control packets to detect link failures and requires efficient forwarding for timely operation. Cisco Express Forwarding (CEF) provides the necessary optimized, hardware-based packet forwarding, making its enablement a prerequisite on all devices participating in BFD sessions.
While BFD integrates with BGP to provide faster fault detection, configuring BGP timers is not a prerequisite for BFD itself; BFD functions independently to detect failures and then notifies BGP.
Concept tested: BFD Configuration Prerequisites
Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bfd/configuration/15-mt/ird-bfd-15-mt-book/ird-bfd-config.html
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