Understanding the backup path calculation
Figure 10.3 illustrates the topology diagram for TI-LFA node protection.
Figure 10.3 – The TI-LFA node protection primary and backup paths
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
Moreover, the backup path is classified as TI-LFA (node) because node protection is explicitly requested in the P2 router configuration.
TI-LFA
In this scenario, the post-convergence path would be P2 - P7 - P4 - PE5 with a cost of 120.
In addressing the node failure on P3, TI-LFA provides node protection by collecting the following information:
- P-Space of P2 along the post-convergence path: The group of routers on the post-convergence path, reachable from
P2through the shortest path tree...
