Step 2: Trace Nodes Visited During CSPF Computations

Purpose

The configuration of the cspf-node flag provides details in the log file about the nodes visited during CSPF computations. The node information is in addition to the overview information provided by the cspf flag. Details about links visited during CSPF computations are not included in the log file.

Action

To trace nodes visited during CSPF computations and to examine the CSPF log file, enter the following JUNOS CLI commands:

[edit protocols mpls]

user@R1# run monitor start filename

user@R1# run show log filename

   
NOTE: To stop monitoring CSPF, issue the monitor stop command. If you are working in configuration mode, as shown in the sample output, issue the run monitor stop command.


 

Sample Output 1

[edit protocols mpls]

user@R1# show 

traceoptions {

    file cspf-node1;

    flag cspf;

    flag cspf-node;

}

label-switched-path R6-to-R1 {

    to 10.0.0.1;

}

interface so-0/0/0.0;

interface so-0/0/1.0;

interface so-0/0/2.0;

interface so-0/0/3.0;

Sample Output 2

[edit protocols mpls]

user@R1# run show log cspf-node1 | no-more 

Apr 29 13:39:08 trace_on: Tracing to "/var/log/cspf-node1" started

Apr 29 13:40:43 RPD_MPLS_LSP_DOWN: MPLS LSP R1-to-R6 down on primary()

Apr 29 13:40:43 RPD_MPLS_PATH_DOWN: MPLS path down on LSP R1-to-R6

Apr 29 13:40:43 CSPF adding path R1-to-R6(primary) to CSPF queue 1

Apr 29 13:40:43 CSPF creating CSPF job

Apr 29 13:40:43

Apr 29 13:40:43 CSPF for path R1-to-R6(primary), begin at R1.00, starting

Apr 29 13:40:43         bandwidth: CT0=0bps; setup priority: 0; random

Apr 29 13:40:43 CSPF final destination 10.0.0.6

Apr 29 13:40:43 CSPF starting from R1.00 (10.0.0.1) to 10.0.0.6, hoplimit 254

Apr 29 13:40:43     Node R1.00 (10.0.0.1) metric 0, hops 0, avail 32000 32000 32000 32000

Apr 29 13:40:43     Node R3.00 (10.0.0.3) metric 10, hops 1, avail 32000 32000 32000 32000

Apr 29 13:40:43     Node R5.00 (10.0.0.5) metric 10, hops 1, avail 32000 32000 32000 32000

Apr 29 13:40:43     Node R2.00 (10.0.0.2) metric 10, hops 1, avail 32000 32000 32000 32000

Apr 29 13:40:43     Node R4.00 (10.0.0.4) metric 20, hops 2, avail 32000 32000 32000 32000

Apr 29 13:40:43     Node R6.00 (10.0.0.6) metric 20, hops 2, avail 32000 32000 32000 32000

Apr 29 13:40:43 CSPF Reached target

Apr 29 13:40:43 CSPF completed in 0.000304s

Apr 29 13:40:43 CSPF ERO for R1-to-R6(primary) (2 hops)

Apr 29 13:40:43         node 10.1.12.2/32

Apr 29 13:40:43         node 10.1.26.2/32

Apr 29 13:40:43 CSPF for R1-to-R6 done!

Apr 29 13:40:43 RPD_MPLS_PATH_UP: MPLS path up on LSP R1-to-R6

Apr 29 13:40:43 RPD_MPLS_LSP_UP: MPLS LSP R1-to-R6 up on primary() Route 10.1.12.2 10.1.26.2

[...Output truncated...]

[edit protocols mpls]

user@R1# run monitor stop 

What It Means

Sample Output 1 shows the configuration of the cspf-node file, cspf flag and cspf-node flag at the [edit protocols mpls traceoptions] hierarchy level. See Configuring CSPF Tracing for steps to configure CSPF tracing.

Sample Output 2 shows the contents of the cspf-node file in the /var/log/ directory on ingress router R1. The cspf-node file contains the CSPF computations logged when the cspf and cspf-node flags are configured at the [edit protocols mpls traceoptions] hierarchy level and after the run monitor start cspf and run show log cspf commands are issued.

Each line of output describes the steps taken by the CSPF algorithm to calculate the shortest path between the ingress and egress routers. Because the cspf-node flag is configured, the output shows the nodes visited during the calculations performed by the CSPF algorithm. For example, all nodes in the network shown in Figure  are included.

The result of the CSPF algorithm is formed into a strict-hop ERO. For example, the ERO for the LSP R1-to-R6 contains two hops that pass through nodes 10.1.12.2/32 and 10.1.26.2.32. When the ERO is completed, CSPF for R1-to-R6 done!, the ERO is passed to the RSVP protocol process, where it is used for signaling and establishing the LSP in the network. The output shows RPD_MPLS_LSP_UP, indicating that the LSP was established successfully.