Examining the CSPF Log File
Purpose
The CSPF log file provides useful information about the steps taken by the CSPF algorithm to calculate the shortest path from the ingress router to the egress router. The following steps and output illustrate the CSPF algorithm in the successful establishment of an LSP. With each flag that you configure, starting with the cspf flag, then the cspf-node flag, and finally the cspf-link flag, more granular information about CSPF calculations is provided by the output in the CSPF log file configured to gather the information.
Figure illustrates the example network topology used in this section. The example MPLS network uses IS-IS Level 2 and a policy to create traffic. However, IS-IS Level 1 or an OSPF area can be used and the policy omitted if the network has existing Border Gateway Protocol (BGP) traffic.
The MPLS network in Figure is a router-only network with SONET interfaces that consist of the following components:
- A full-mesh interior BGP (IBGP) topology, using AS 65432
- MPLS and RSVP enabled on all routers
- A send-statics policy on routers R1 and R6 that allows a new route to be advertised into the network
- Two unidirectional LSPs between R1 and R6, which allow bidirectional traffic
See the JUNOS MPLS Network Operations Guide for information on configuring an MPLS network. The ingress router R1 is configured with CSPF tracing, and the output examined in the following three steps is taken from R1.