Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?

 
 

Leaking BGP-CT Prefixes into Flexible Algorithm

You can now leak BGP-CT prefixes into flex algo and vice-versa.

Figure 1: BGP-CT – Flexible Algorithm Leaking BGP-CT – Flexible Algorithm Leaking

For example, the topology shown in #id-understanding-isis-flexible-algorithm-for-segment-routing consists of multiple IS-IS IGP instances. The ISIS-A has flex algo but does not have BGP-CT. In such deployments, BGP-CT prefixes can be leaked into flex algo and vice-versa via policy configurations.

Currently, BGP-CT prefixes do not support carrying the prefix-SID information. Configure a policy for the prefix and associate a prefix-SID on the router that is redistributing the prefix into IS-IS flex algo.

When flex algo prefix-SIDs are leaked from BGP-CT, FAPM sub-TLV will be advertised with the metric derived from the export policy or the route’s metric. The Metric defined in the export policy has higher precedence over the route’s metric. Additionally, IS-IS installs a stitched route in the mpls.0 tables to stitch the incoming MPLS traffic from BGP-CT to IS-IS.