Understanding backup path calculation
The following topology diagram describes the backup path calculation.
Figure 12.2 – TI-LFA Global Weighted SRLG protection primary and backup path
The following explanation details the computation and selection of the primary path and backup path.
Primary path
The primary path from P2 to PE5 goes via P3, with the end-to-end path, cost of 30 (P2 - P3 - P4 - PE5), making it the shortest path.
Backup path
The backup path is classified as TI-LFA (srlg) because SRLG protection is explicitly requested in the P2 router configuration
TI-LFA
The post-convergence path in the scenario, including the local srlg-disjoint request, would be P2 - P6 - P7 - P4 - PE5, with a cost of 220.
In addressing the link failure on the P2–P3 link, TI-LFA provides SRLG protection by collecting the following information:
- P-Space of P2 along the post-convergence path: The group of routers on the post-convergence...
