This article describes an issue in which a newly configured label switched path (LSP) does not change to the 'Up' state, due to the LSP path traversing multiple areas or autonomous systems (ASs). To allow the LSP to change to the 'Up' state in a multiple area LSP path, a router must be able to perform a route lookup in the Interior Gateway Protocol (IGP) database. To permit this, the inter-domain parameter must be configured.
When configuring LSPs which will traverse multiple areas or ASs, a router may be unable to locate a path using intra-domain Constrained Shortest Path First (CSPF) lookup.
Intra-domain CSPF route lookups using in the traffic engineering database (TED) may result in a router being unable to find a route where multiple areas or ASs comprise the path an LSP must take to reach the configured destination.
To allow the LSP to change to the 'Up' state in a multiple area LSP path, a router must be able to perform a route lookup in the IGP database. In order to allow the router to perform an IGP lookup for a multi-area LSP, the following parameter must be configured:
inter-domain
This parameter can be configured in the following hierarchies:
[edit protocols mpls label-switched-path label-switched-path-name]
[edit logical-systems logical-system-name protocols mpls label-switched-path label-switched-path-name]
This parameter allows the router to search the IGP database and complete the LSP path lookup. The LSP should change to the 'Up' state.