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How to Trace IS-IS Protocol Traffic in Juniper
 
You are setting up IS-IS on your network and want to keep a running log of IS-IS protocol packets that the router is sending to help you track any problems that might occur during the configuration process.
Set up a tracing file that captures information about IS-IS protocol operations:
 
[edit protocols isis]
source@RouterJ# set traceoptions file isis-logs
source@RouterJ# set traceoptions flag error
source@RouterJ# set traceoptions flag general
source@RouterJ# set traceoptions flag normal
 
To stop the tracing, remove the traceoptions statement from the configuration:
 
[edit protocols isis]
source@RouterJ# delete traceoptions
 
To debug IS-IS operations, use the JUNOS tracing facility to track the packets that IS-IS is sending and receiving. You specify the name of the file to which you want to collect the information and the type of information you want to trace. In this example, we set three flags to track normal operations and errors in the file isis-logs, which is on the router's hard disk in the directory /var/log (on M-series and T-series routers) and /cf/var/log (on J-series routers).
 
When you are first bringing up an IS-IS network, you may find that an adjacency is not establishing between two Level 1 routers:
 
source@RouterJ> show isis adjacency
Interface             System          L State       Hold (secs) SNPA
ge-0/0/1.0            RouterF         1 Down                 0 0:5:85:c1:86:31
ge-1/0/0.0            RouterC         2 Up                  22 0:5:85:c1:d1:f4
ge-1/0/1.0            RouterA         2 Up                  24 0:5:85:c2:2e:f5
 
The logfile shows where the problem is:
 
source@RouterJ> show log isis-logs | last
Aug 12 12:47:15 ERROR: IIH from RouterA with no matching areas, interface ge-1/0/1.0
Aug 12 12:47:15     local area 49.0050
Aug 12 12:47:15     remote area 49.0020 (3 bytes)
Aug 12 12:47:15 ERROR: IIH from RouterF with no matching areas, interface ge-0/0/1.0
Aug 12 12:47:15     local area 49.0050
Aug 12 12:47:15     remote area 49.0051 (3 bytes)
 
The second error shows that the adjacency to the Level 1 router RouterF is down because RouterJ is in Area 50, while RouterF has been accidentally misconfigured to be in Area 51. You might wonder why we are not concerned with the first error in the file, which also reports an area mismatch. We don't care about this because RouterA is another Level 2 router and is in a different area (Area 20), so it's fine for it to have a different area number.
 
Over time, the IS-IS logfiles can become very large and fill up the router's hard disk. To save the logfile for future analysis, you can copy the file to a server:
 
source@RouterJ> file copy /cf/var/log/isis-logs server1:isis-logs-20050625
 
If you no longer need the information in the file, you can delete the contents:
 
source@RouterJ> clear log isis-logs
 
Deleting the file's contents does not turn off tracing.
 
To stop the tracing altogether, you can remove the traceoptions statement from the configuration with the delete traceoptions command or you can leave the statements in the configuration and simply deactivate them so that they do not take effect when you commit the configuration:
 
[edit protocols isis]
source@RouterJ# deactivate traceoptions
 
To delete the logfiles and the rolled-over version of the file, use the file delete command:
 
source@RouterJ> file delete isis-logs*
 
When debugging IS-IS, you can set one or more of the following trace flags to capture IS-IS information:
 
[edit protocols isis traceoptions]
source@RouterA# set flag ?
Possible completions:
  all                  Trace everything
  csn                  Trace complete sequence number (CSN) packets
  error                Trace errored packets
  general              Trace general events
  graceful-restart     Trace graceful restart events
  hello                Trace hello packets
  lsp                  Trace link-state packets
  lsp-generation       Trace LSP generation
  normal               Trace normal events
  packets              Trace  
IS-IS packets
  policy               Trace policy processing
  psn                  Trace partial sequence number (PSN) packets
  route                Trace routing information
  spf                  Trace SPF events
  state                Trace state transitions
  task                 Trace routing protocol task processing
  timer                Trace routing protocol timer processing
 
Using some of the other flags, you can see IS-IS protocol packet exchanges:
 
Aug 12 16:11:31 Sending L2 CSN on interface ge-1/0/0.0
Aug 12 16:11:31     LSP range 0000.0000.0000.00-00 to ffff.ffff.ffff.ff-ff
Aug 12 16:11:31     packet length 131
Aug 12 16:11:31 Received L1 LAN IIH, source id RouterC on ge-1/0/0.0
Aug 12 16:11:31 ERROR: IIH from RouterC with no matching areas, interface ge-1/0/0.0
Aug 12 16:11:31     local area 49.0050
Aug 12 16:11:31     remote area 49.0030 (3 bytes)
Aug 12 16:11:31 ISIS L2 periodic xmit to 01:80:c2:00:00:15 interface ge-1/0/1.0
Aug 12 16:11:31 ISIS L2 periodic xmit to 01:80:c2:00:00:15 interface ge-1/0/0.0
Aug 12 16:11:31 ISIS L2 hello from RouterC interface ge-1/0/0.0 absorbed
Aug 12 16:11:32 Sending L2 CSN on interface ge-1/0/1.0
Aug 12 16:11:32     LSP range 0000.0000.0000.00-00 to ffff.ffff.ffff.ff-ff
Aug 12 16:11:32     packet length 131
Aug 12 16:11:32 Sending L1 CSN on interface ge-0/0/1.0
Aug 12 16:11:32     LSP range 0000.0000.0000.00-00 to ffff.ffff.ffff.ff-ff
Aug 12 16:11:32     packet length 83
Aug 12 16:11:32 Received L1 LAN IIH, source id RouterA on ge-1/0/1.0
Aug 12 16:11:32 ERROR: IIH from RouterA with no matching areas, interface ge-1/0/1.0
Aug 12 16:11:32     local area 49.0050
Aug 12 16:11:32     remote area 49.0020 (3 bytes)
Aug 12 16:11:33 ISIS L1 hello from RouterF interface ge-0/0/1.0 absorbed
Aug 12 16:11:33 ISIS L1 periodic xmit to 01:80:c2:00:00:14 interface ge-0/0/1.0
Aug 12 16:11:33 ISIS L2 hello from RouterA interface ge-1/0/1.0 absorbed
 
This logfile snippet shows that IS-IS exchanges complete sequence number (CSN) LSPs with one of its Level 2 and one of its Level 1 neighbors. You also see the periodic transmission of IS-IS Hello packets.
 
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