A specific LSP can be selected as transport to a specified BGP next hop for BGP labeled unicast and unlabeled BGP routes tunneled over RSVP and SR-TE LSPs.
Routes are imported via import route policies. Named routing policies may contain route admin-tag policies. For route import policies that contain route admin-tag policies, the set of available RSVP and SR-TE LSPs in TTM are first pruned as described in Internal Route Color to LSP Color Matching Algorithm.
This set may then be further reduced by a resolution filter.
If weighted-ecmp is configured, then this is applied across the resulting set.
Routes with no admin-tag can still resolve to any tagged or untagged LSP. It is possible that, following the resolution filter, no eligible RSVP or SR-TE LSP exists. By default, the system falls back to using LDP, SR-ISIS, SR-OSPF, or any other lower-priority tunnel type; otherwise the resolution fails. That is, matching admin-tagged RSVP or SR-TE LSPs are preferred to other LSP types. On a per-address family basis, the enforce-strict-tunnel-tagging command in the next-hop-resolution filter for BGP labeled routes or shortcut tunnels can be used to enforce that only tagged tunnels are considered; otherwise, resolution fails.