Summary
In order to explore the single-segment FRR scenario, the lab topology in Figure 7.1 required modifications to ensure that the Zero-Segment FRR path was unavailable. Building on the previous lab setup, several strategic interfaces were shut down to achieve the desired topology suitable for single-segment FRR exploration.
The verification steps on the P2 router revealed a backup path that included an additional segment directing traffic to the P8 router before reaching the destination router PE5. This was confirmed through the label stack outputs observed in the RIB, LFIB, and FIB.
Although the lab used a small topology where visual inspection sufficed to determine the TI-LFA post-convergence path, such visual inspection is impractical in production networks with hundreds of routers and thousands of links. So, the calculation of the TI-LFA backup path was then detailed, focusing on the P-Space and extended-P-Space of P2 and the Q-Space of PE5 to identify overlapping routers...
