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Examine the CSPF Log File

 

Purpose

After you have confirmed that the LSP is down, obtain more information about the possible cause of the failure.

Note

To obtain useful information from the CSPF log file, make sure that CSPF tracing is configured on the ingress router.

Action

To examine the CSPF log file, enter the following Junos OS CLI operational mode commands:

Note

To stop monitoring CSPF, issue the monitor stop command.

Sample Output

Meaning

The sample output shows that the monitor start cspf command was issued to start displaying entries in the cspf log file in real time. The cspf log file is generated by the routing protocol process after the file is configured with the traceoptions statement at the [edit protocols mpls] hierarchy level. In this example, the cspf log file is configured with the cspf, cspf-node, and cspf-link flags to provide the most granular information about the steps taken by the CSPF algorithm.

The only link that passes the color constraint is between R1 and R5, 10.1.15.0/32. The CSPF algorithm is a locally run algorithm, which makes its calculations on a given router. When the CSPF algorithm runs on R5, it prunes 10.1.15.2 and selects 10.1.56.1 to send the message to R6.The link between R5 and R6 10.1.56.0/32 does not pass the color constraints, indicating a problem with R5. At this stage, it is useful to examine the traffic engineering database to determine which link on R5 should be associated with the red color.