352-001 · Question #297
Which option is a BFD design consideration?
The correct answer is B. BFD echo mode may reduce convergence time.. BFD echo mode offloads failure detection to the data plane by looping echo packets through the remote forwarding path, enabling shorter detection intervals and reduced convergence time.
Question
Which option is a BFD design consideration?
Options
- ABFD should not be used with RSVP-TE backup tunnels.
- BBFD echo mode may reduce convergence time.
- CBFD does not support sessions over MPLS LSPs.
- DBFD is supported on indirectly connected peers.
How the community answered
(19 responses)- A5% (1)
- B89% (17)
- D5% (1)
Why each option
BFD echo mode offloads failure detection to the data plane by looping echo packets through the remote forwarding path, enabling shorter detection intervals and reduced convergence time.
BFD is commonly paired with RSVP-TE backup tunnels to provide fast failure detection that triggers TE tunnel switchover, making this combination a valid and widely deployed design pattern.
In BFD echo mode, a router sends echo packets that are looped back by the remote peer's forwarding plane without involving the remote control-plane CPU, allowing the local system to use shorter detection intervals than standard asynchronous BFD. Because failure detection is handled locally and at line rate, the interval between a link failure and routing protocol reconvergence is reduced.
BFD does support sessions over MPLS LSPs - RFC 5884 specifically defines BFD for MPLS Label Switched Paths as a supported and deployed capability.
Standard BFD requires directly connected peers; while multihop BFD (RFC 5883) extends support to indirectly connected peers, stating that BFD generically supports indirectly connected peers misrepresents standard single-hop BFD behavior.
Concept tested: BFD echo mode and convergence design considerations
Source: https://www.rfc-editor.org/rfc/rfc5880
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