Source Packet Routing in Networking (SPRING) or Segment Routing

Static route resolution over SR-TE tunnel (MX Series and PTX Series)—Starting in Junos OS Release 21.2R1, we support static route resolution over segment routing–traffic engineered (SR-TE) colored and uncolored label-switched paths (LSPs). To enable this feature, configure the spring-te-lsp-next-hop statement at the [edit routing-options static destination] and [edit routing-options rib rib name static destination] hierarchy levels. The feature support extends towards static, DTM, BGP-SR-TE, and PCEP source types that are currently supported by Source Packet Routing in Networking–Traffic Engineering (SPRING-TE). If a source is not configured, by default, it takes the next hop as static.

You must configure the tunnel-tracking statement at the [edit protocols source-packet-routing] hierarchy level to enable this feature. This feature enhances the accuracy of first-hop label-based tunnel status for SR-TE tunnels according to their route resolution.

[See spring-te-lsp-next-hop and source-packet-routing.]

Express segments using SR-TE underlay (MX Series and PTX Series)—Starting in Junos OS Release 21.2R1, we’ve introduced SR-TE underlay path support for express segments to enable end-to-end transport of segment routing–traffic engineered (SR-TE) label-switched paths (LSPs) for very large multi-domain networks. The path is automated using segment-set or template policies for uncolored or colored segment routing policies. The rib-group configuration is required to import addresses to inet.3 for colored segment routing policies. When the express segments underlay is colored SR-TE, you need to configure the no-chained-composite-next-hop statement at the [edit protocols source-packet-routing] hierarchy level for the express segment to install the correct flattened next hop.

This feature has the following limitations:

• When the express segments underlay is colored SR-TE, the express segment does not inherit the SR-TE LSP underlay attributes (SR-TE name, metric).
• The install-nexthop option at the [edit policy-options policy-statement policy-name term term-name then] hierarchy level to filter a specific SR-TE LSP bu its name is not supported.
• Express segments do not consider the respective weights of the primary and secondary segment lists of SR-TE LSP. Secondary LSP segments can be preferred for traffic even when the primary segment is up.

[See Express Segment LSP Configuration.]