Junos Cup 2014
Junos Cup 2014

Tournament 2: Spain Challenge & Solution: Traffic Engineering Constraints

[ Edited ]
‎06-19-2014 07:32 AM

Country Flag: SPAIN


Author: Antonio Sánchez Monge


Title: Traffic Engineering Constraints


Type: Service Provider


Difficulty: High (2 points).


Technical Description: Strengthen the network design so that if any single backbone link goes down, the service recovers automatically in a few seconds.




Challenge Instructions:

For this challenge, you need to start the topology called: “SPAIN – Traffic Engineering Constraints”.


This scenario was originally conceived for multicast but, for simplicity, it has been ported to unicast. There is a central site (number 1, on top), and two branch sites (number 2 and 3, lower left and lower right, respectively).


For bandwidth restrictions in the backbone links, PE1A is only authorized to inject traffic in the red direction (counter-clockwise), and PE1B only in the blue direction (clockwise). In this challenge, you are not allowed to change these requirements.


At any time, you can verify end-to-end connectivity by executing from CE1:


ping source

ping source


The Network Operation Center (NOC) told you that, when one single backbone link goes down for one hour, sometimes the service recovers very quickly, but other times there is one hour of service disruption towards one of the branch sites. The NOC suspects that certain backbone links are not protected in the sense that, if they go down, the “blue” and “red” flows are both affected.


You need to fix this situation with just two configuration commands. What does “two configuration commands” mean? Either the following sequence in just one router:



<command1>  /* load is not permitted */

<command2>  /* load is not permitted */

commit and-quit


Or the following sequence in two different routers (the command can be different on each one):



<command>  /* load  is not permitted */

commit and-quit


These are the conditions you need to meet:


-       You are not allowed to loosen the traffic engineering requirements at site 1: PE1A injects on red, and PE1B injects on blue.

-       If backbone link “x” remains down for one hour, the service (ping) should recover automatically in less than two minutes (normally much less). This should be true for any of the backbone (inter-PE) links, with no exception.

-       If, during the time that link “x” is down, another link “y” flaps (in the sense that “y” transitions up->down->up, being down for less than 10 seconds), the service should recover automatically in less than two minutes. This should be true for any pair of backbone links.

-       If one single PE in the network goes down, the service should be restored automatically. In the case where two PEs in the network go down, though, recovery is NOT always guaranteed.

-       The total number of configuration lines in each PE should not vary. In other words, for a given PE, the final configuration should have no more, no less lines than the initial configuration.


To solve this challenge submit the two allowed set commands and at which router(s) they are issued.


NOTE: If you have issues connecting to the Junosphere topology please check Junosphere Technical documentation, or request assistance in the Junosphere forum 


Send an email with your proposed solution to junos-cup@juniper.net:

  •  The subject should be “<country-name-of-the-challenge> -  <your-full-name>”. For example: “Brazil – Wolfgang Amadeus Mozart”.
  • In the email body, please include your proposed solution, along with your first and last name and complete mailing address including zip/postal code and your shirt size (S, M, L, XL, XXL, XXXL) (Only if you haven’t already submitted your address/shirt size on a previous submission)


Deadline to Respond: Tuesday, 24th of June 23:59:59 Pacific Daylight Time (PDT)

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Some additional notes:

  • You can try to solve and submit answers for as many active challenges as you wish
  • The answers will be read by the organization right after the deadline
  • The challenge instructions are final, and no additional information or tips will be provided before the publication of the solution and the winner list. Please don’t expect a reply from junos-cup@juniper.net.
  • If you feel that your initial solution is wrong or incomplete, you can send up to three messages for the same challenge, but please note that only your last message (received before the deadline) will be read.
  • If you think there is an error in the definition of the challenges, please send us an email with subject (“<country-name> ERROR”); if there is no reply, then it’s likely an intentional condition of the challenge, rather than an error.



Revert the route target assignments in PE3A and PE3B:

juniper@PE3A# set routing-instances myVRF vrf-target target:65000:2

juniper@PE3B# set routing-instances myVRF vrf-target target:65000:1


The idea is that the blue path enters a remote site through the blue PE. And the red path enters a remote site through the red PE.




Julie Wider
Advocacy Manager
Twitter: @JNetCommunity & @jawider