Profile 28 w/ Constraints and FRR
Continuing on from the previous lab, configure the default MDTs to exclude RED links and use FRR. Color the XR1-XR3 link red.
Answer
Explanation
In profile 27 (static p2mp policies), the policy was configured directly on the PCE, so the constraints and FRR was configured there as well.
In profile 28 and 29, FRR and constraints are configured on the PEs. These affect only the p2mp policies for which they act as a root. (The PE only asks the PCE for path computation for p2mp policies for which it is the root).
To configure constraints, you must create a normal on-demand SR-TE policy, and then associate that color with the default MDT. Additionally, FRR is enabled on the default MDT.
This lab asks us to avoid link color RED. On the PEs, we must add an ODN policy as follows. Any color can be used. Also note that we could have choosen another metric type besides igp.
This color is associated with the default MDT for SR. Additionally, FRR is enabled for the default MDT.
If we look at the policy on the PCE, we can see that FRR is enabled, and the affinity constraint was signaled. Note that all the nexthops have an exclamation point, indicating FRR is in use.
This is also reflected on the PE. Note the outgoing interface is “none” as TI-LFA is used to find the outgoing interface now.
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