ScreenOS Firewalls (NOT SRX)
Trusted Expert
Posts: 441
Registered: ‎07-08-2008

Troubleshooting Tips - Debug commands

[ Edited ]

There are many debug commands that you can run to troubleshoot problems on Juniper firewalls. The most common debugs used are:


Debug flow basic
shows the flow of traffic through the firewall, allowing for troubleshooting route selection, policy selection, any address translation and whether the packet is recieved or dropped by the firewall.


Debug ike detail
show all of the vpn messages between two devices when setting up the vpn. Useful to see problems between Juniper and 3rd party firewalls or configuration porblems.


Other debugs are ones allowing troubleshooting of routing protocols, av, deep inspection, higher availability, NAT and loads of others. You can find out what others there are by typing 'debug ?' on the cli.


Debug captures are sent to a buffer by default but can be sent the console.


Buffer commands:
     get dbuf info        - Displays debug buffer size in bytes

     get dbuf stream  - Displays the contents of the debug buffer

     set dbuf size       - Allocates system memory for the debug buffer

     clear dbuf            - Clears the contents of the debug buffer



Here are best practices when debug flow basic and how to read the output.


Debug Flow basic


    1)   get ffilter - see if an filters have been set already, if they have you use 'unset ffilter' to remove


    2)   set ffilter - allows you to limit the traffic that you capture using src-ip, src-port, dst-ip, dst-port, ip-proto Recommeded as debug flow basic can be intensive on the firewall especially if it is under heavy load.


     filters that are written on one line are and 'AND' statement. eg set ffilter scr-ip dst-ip will match AND


     filters that are on seperate lines are 'OR' statements. eg set ffilter scr-ip, set ffilter dst-ip will match  OR


    3)   debug flow basic - turns on flow debuging with a level of basic logging


    4)   clear db - make sure there is nothing in the debug buffer from previous debugs


    5)   Begin the test, do a ping or try to access the resource that you are having problems with.


    6)   undebug all or press Esc key - turns off debug


    7)   get db str - reads the debug buffer and outputs it to the screen for reading.


    8)   unset ffilter - remove ffilters when finished


Juniper Firewall Packet Process


Packet Process



Reading a Debug Flow Basic


FW-> get dbuf stream
****** 15625.0: <private/ethernet0/5> packet received [60]****** - This is the interface and zone that the packet arrives on
  ipid = 34344(8628), @02cdf8b0
  packet passed sanity check.
  ethernet0/5:>,1(8/0)<Root> - This is the packet IP info ports and protocol
  no session found - Looks for existing sessions on the firewall
  flow_first_sanity_check: in <ethernet0/5>, out <N/A>
  chose interface ethernet0/5 as incoming nat if. - There is NAT on the interface
  flow_first_routing: in <ethernet0/5>, out <N/A>
  search route to (ethernet0/5,> in vr trust-vr for vsd-0/flag-0/ifp-null
  [ Dest] 10.route>, to ethernet0/6 - matches route 10 in the trust-vr routing table
  routed (x_dst_ip from ethernet0/5 (ethernet0/5 in 0) to ethernet0/6
  policy search from zone 104-> zone 103 - Tells you which policy set its going to look at zone to zone derived from routing
 policy_flow_search  policy search nat_crt from zone 104-> zone 103
  RPC Mapping Table search returned 0 matched service(s) for (vsys Root, ip, port 2396, proto 1)
  No SW RPC rule match, search HW rule
  Permitted by policy 2 - Tells you which policy the traffic has hit and what the action is
  No src xlate   choose interface ethernet0/6 as outgoing phy if
  no loop on ifp ethernet0/6.
  session application type 0, name None, nas_id 0, timeout 60sec
  service lookup identified service 0.
  flow_first_final_check: in <ethernet0/5>, out <ethernet0/6>
  existing vector list 1-4339cf0.
  Session (id:8061) created for first pak 1 - session created for future packes in the session
  route to
  arp entry found for - firewall arps for where it is going to route packet to.
  nsp2 wing prepared, ready
  cache mac in the session
  search route to (ethernet0/6,> in vr trust-vr for vsd-0/flag-3000/ifp-ethernet0/5
  [ Dest] 12.route>, to ethernet0/5
  route to
  flow got session.
  flow session id 8061
  post addr xlation:> - shows if there has been and address translation and how the packet looks when it is sent out.



Things to look for when there are problems:


Packet dropped, no route to host - no route has been round in the virtual router that the interface and zone is bound to that the packet arrived on. You need to look in your routing table to check to see if you have a route for the desitnaiton or source depending how you are routing.


Packet dropped, denied by policy - If just before this you see a message saying searching global policy then it means that no policy has been matched so it has been dropped by default. You need to check your policy configuration.


Policy match  - Check the policy matach to make sure that it is matching the right polic and not doing allowed or denied by another rule


Also check to make sure any NAT is happening that needs to.


If this has been of use then give it kudos and I will look to write more


Post a message on any suggestions of topics you would like covered, either troubleshooting, configuration or explinaiton of features.





Message Edited by AndyC on 08-22-2008 09:03 PM
Message Edited by AndyC on 08-22-2008 09:04 PM
Message Edited by AndyC on 08-27-2008 09:42 PM
Message Edited by DJoshi on 05-04-2009 04:58 PM
Message Edited by DJoshi on 05-04-2009 04:58 PM
Message Edited by DJoshi on 05-04-2009 04:59 PM
Distinguished Expert
Posts: 414
Registered: ‎06-18-2008

Re: Troubleshooting Tips - Debug commands



would like to share above link, very useful for configuration/troubleshooting of Firewall VPN.



Raheel Anwar


Follow me on Twitter @anwar_raheel

If this post was helpful, please mark this post as an "Accepted Solution".
Kudos are always appreciated!
Trusted Expert
Posts: 441
Registered: ‎07-08-2008

Re: Troubleshooting Tips - Debug commands

Thanks raheel, forgot to add that in.





Posts: 33
Registered: ‎07-08-2008

Re: Troubleshooting Tips - Debug commands

extremely helpful post


thanks Andy and Raheel


- Ray 

Posts: 45
Registered: ‎08-23-2008

Re: Troubleshooting Tips - Debug commands

Thanks AndyC now I will post that VPN log information you asked for in my post! At first when you asked me for it I was like man how the heck do I do that then I remembered seeing your post on here and took a look. Very nice. Thanks. Man Wink
Posts: 6
Registered: ‎09-30-2008

Re: Troubleshooting Tips - Debug commands

Thanks AndyC.


This post is very helpful.

Trusted Contributor
Trusted Contributor
Posts: 98
Registered: ‎11-07-2007

Re: Troubleshooting Tips - Debug commands

Hi Andy,


Great contribution! Well deserved kudos :-)


One small detail remark: from the block “Dest reachable?” the Yes arrow should go to “Crossing zones/inter-zone block”, in stead of going to "policy lookup" directly.

Just my 2 cents...





Recognized Expert
Posts: 258
Registered: ‎11-06-2007

Re: Troubleshooting Tips - Debug commands

[ Edited ]


Thank you for this post!


Can you also add a link to the following KB article, perhaps at the end of the Debug Flow Basic section?

KB12208 - 'debug flow basic' Example



Message Edited by PentinProcessor on 05-04-2009 07:39 AM
Distinguished Expert
Posts: 2,397
Registered: ‎01-29-2008

Re: Troubleshooting Tips - Debug commands

Hi - was trying to access this link through the Forum and it comes up empty. Thought you should know it appears to be broken.


Kevin Barker
Juniper Networks Certified Instructor
Juniper Networks Ambassador

Juniper Elite Reseller
J-Partner Service Specialist - Implementation

If this worked for you please flag my post as an "Accepted Solution" so others can benefit. A kudo would be cool if you think I earned it.
New User
Posts: 1
Registered: ‎04-01-2009

Re: Troubleshooting Tips - Debug commands

The debug flow KB is available here
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