Configuring Path Calculation

Context

To calculate a tunnel path meeting specified constraints, CSPF should be configured on the ingress.

CSPF extends the shortest path first (SPF) algorithm and is able to calculate the shortest path meeting MPLS TE requirements. CSPF calculates paths using the following information:

Link state information sent by IGP-TE and saved in TEDBs
Network resource attributes, such as the maximum available bandwidth, maximum reservable bandwidth, and affinity property, sent by IGP-TE and saved in TEDBs
Configured constraints such as explicit paths

An RSVP-TE tunnel can be established on a CSPF-disabled ingress. However, to allow a path to meet tunnel constraints, you are advised to enable CSPF on the ingress before establishing the RSVP-TE tunnel.
Enabling CSPF on all transit nodes is recommended. The tunnel function fails if CSPF or IGP TE is not enabled on the ingress, IGP TE is not enabled on some transit nodes or the egress, and CSPF is enabled on some transit nodes.

Perform the following configurations on the ingress node of an MPLS TE tunnel.

Procedure

Run system-view
The system view is displayed.
Run mpls
The MPLS view is displayed.
Run mpls te cspf
CSPF is enabled on a node.

CSPF is disabled by default.
(Optional) Run mpls te cspf preferred-igp { isis [ isis-process-id [ level-1 | level-2 ] ] | ospf [ ospf-process-id [ area { area-id-1 | area-id-2 } ] ] }
A preferred IGP is specified.

By default, OSPF is preferred for CSPF path calculation.

If a single IGP protocol is only configured on the backbone network to advertise OSPF or IS-IS TE information, ignore this step.