BGP On-Demand Next Hop and Auto Steering
This chapter contains configurations of BGP on-demand next hop (ODN) and auto steering with segment routing.
SR Policy is identified by three main components which are: Headend, Endpoint and Color.
When redistributing routing information across domains, provisioning of multi-domain services (Layer 2 VPN and Layer 3 VPN) has its own complexity and scalability issues.
Segment Routing On-Demand Next Hop (ODN) or SR TE auto steering triggers delegation of computation of an end-to-end LSP using dynamic computation (isis/ospf/pcep) including constraints and policies without doing any redistribution. It then installs the reapplied multi-domain LSP for the duration of the service into the local forwarding information base (FIB).
Coloring plays very important role in automated steering solution. Color information is exchanged by BGP extended community attribute (sub tlv) and BGP tunnel encapsulation attribute in the VPN route UPDATE messages. Egress PE node colors the service routes (VPN routes), advertises to ingress PE with colors that signifies SRTE SLA requirement. Ingress node uses this color to match SR policy, once node identifies SR policy by matching color, it automatically steers traffic onto the SR policy. This is called Automated Steering.
Last modified date: 10/20/2023