352-001 · Question #561
Which two options are benefits of using Topology Independent Loop-Free Alternate in WAN design? (Choose two)
The correct answer is A. It provides backup convergence for all topologies by avoiding the post-convergence path E. It can provide backup paths for IPv4, IPv6 and LDP traffic. TI-LFA (Topology Independent Loop-Free Alternate) provides pre-computed backup paths that work across all topologies and support multiple traffic types without requiring full segment routing deployment as the forwarding plane.
Question
Which two options are benefits of using Topology Independent Loop-Free Alternate in WAN design? (Choose two)
Options
- AIt provides backup convergence for all topologies by avoiding the post-convergence path
- BIt maximizes the network utilization by load-sharing across low bandwidth and edge links while
- CNo additional protocols are required in the MPLS network because it uses LDP labels to signal
- DAlthough it requires enabling segment routing, SR does not have to be activated as the preferred
- EIt can provide backup paths for IPv4, IPv6 and LDP traffic
How the community answered
(30 responses)- A70% (21)
- B10% (3)
- C17% (5)
- D3% (1)
Why each option
TI-LFA (Topology Independent Loop-Free Alternate) provides pre-computed backup paths that work across all topologies and support multiple traffic types without requiring full segment routing deployment as the forwarding plane.
TI-LFA computes backup paths that are guaranteed loop-free for any topology by using the post-convergence path as the repair path, ensuring 50ms fast-reroute coverage regardless of topology shape or size.
TI-LFA is a fast-reroute protection mechanism, not a load-sharing tool - it does not distribute traffic across low-bandwidth or edge links for utilization purposes.
TI-LFA requires segment routing SR labels (not LDP) to encode the backup path, so SR must be enabled in the MPLS network.
While SR does not need to be the preferred forwarding plane for all traffic, this description is not a primary design benefit of TI-LFA and is not among the recognized top advantages for WAN design.
TI-LFA can protect IPv4 unicast, IPv6 unicast, and LDP-labeled traffic using a single unified repair mechanism, making it a versatile solution for mixed-protocol WAN environments.
Concept tested: TI-LFA fast-reroute benefits in WAN design
Source: https://www.cisco.com/c/en/us/td/docs/routers/crs/software/crs_r6-1/segment_routing/configuration/guide/b-segment-routing-crs-r61/b-segment-routing-crs-r61_chapter_010.html
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