Objective

The objective of this chapter is to explore a zero-segment FRR scenario, in which the computed backup path enables fast rerouting without requiring an additional segment encoded as a label. This is achieved through the following tasks:

1. Changing the topology to create a non-ECMP path from P2 to PE5
2. Verifying that a zero-segment backup path is computed and added to the RIB, FIB, and LFIB.

In Figure 6.1, the link between P2 and P3 is marked with a cross. This indicates that when the link from P2 to P3 fails, the TI-LFA mechanism should protect the traffic traversing the P2–P3 link by quickly rerouting it to an alternative path.

Figure 6.1 – Zero-segment FRR

To facilitate this, TI-LFA on P2 already calculates and installs the backup path for such potential failures in the network.

Next, we will adjust the configuration on the routers to reflect the topology described in Figure 6.1.