Precompute a path around the failure
TI-LFA uses a link-state IGP and Segment Routing to preinstall backup forwarding at the point of local repair. It computes reachability after excluding the protected resource and can build a list of segments to steer traffic around the failure. The list can follow the expected post-convergence path.
When the failure is detected, the router can use the repair before the rest of the network finishes converging. The repair applies to protected destinations or segments. It can be encoded for the SR-MPLS or SRv6 data plane.
What the repair protects
Link protection excludes one link. Node protection excludes the neighboring router. Shared Risk Link Group (SRLG) protection excludes links that can fail together. Each mode needs a surviving path that avoids the relevant resource and fits the platform’s forwarding capabilities.
RSVP-TE FRR relies on a signaled backup LSP for protected tunnels. TI-LFA can use a locally computed repair list without signaling a separate RSVP-TE bypass.
Try it in a lab
- In a TI-LFA-capable lab, build two routed paths toward the same destination. Enable a protection mode and check the preinstalled repair next hop and any segment list.
- Send traffic along the primary path and fail the protected resource. Observe the repair path at the adjacent router and verify that traffic resumes or continues as the IGP converges.
- Compare a link-only repair that can still traverse the next-hop router with a node-protecting repair. Fail the next-hop router in the lab and confirm that the selected node repair avoids it.