SR-TE LSP Paths using Explicit SIDs

SR OS supports the ability for SR-TE primary and secondary paths to use a configured path containing explicit SID values. The SID value for an SR-TE LSP hop is configured using the sid-label command under configure>router>mpls>path as follows:

configure router mpls
         path <name>
            [no] hop <hop-index> sid-label <sid-value>

Where sid-value specifies an MPLS label value for that hop in the path.

When SIDs are explicitly configured for a path, the user must provide all of the necessary SIDs to reach the destination. The router does not validate whether the whole label stack provided is correct other than checking that the top SID is programmed locally. A path can come up even if it contains SIDs that are invalid. The user or controller programming the path should ensure that the SIDs are correct. A path must consist of either all SIDs or all IP address hops.

A path containing SID label hops is used even if path-computation-method {local-cspf | pce} is configured for the LSP. That is, the path computation method configured at the LSP level is ignored when explicit SIDs are used in the path. This means that the router can bring up the path if the configured path contains SID hops even if the LSP has path computation enabled.

Note: When an LSP consists of some SID label paths and some paths under local-CSPF computation, the router cannot guarantee SRLG diversity between the CSPF paths and the SID label paths because CSPF does not know of the existence of the SID label paths because they are not listed in the TE database.

Paths containing explicit SID values can only be used by SR-TE LSPs.