Junos Cup 2014
Junos Cup 2014

Tournament 2: Uruguay Challenge & Solution: Ping on Virtual Routers

[ Edited ]
‎06-19-2014 07:35 AM

Country Flag: Uruguay


Author: Antonio Sánchez-Monge


Title: Ping on Virtual Routers


Type: Enterprise


Difficulty: Medium (1 point).


Technical Description: Make a one-hop ping work between a VR in R1 and a VR in R2, with just two set configuration commands.





Challenge Instructions:

For this challenge, you need to start the topology called: “URUGUAY – Ping on a Virtual Router”.


As you solve this challenge, leave a ping command running from R1 to R2:


juniper@R1> ping routing-instance myVR

PING ( 56 data bytes


Initially, it fails. You need to make it work under the following conditions:

-       You can add new configuration lines, but you are not allowed to change the existing configuration lines. In other words, the output of “show configuration | display inheritance | display set” command may display new lines, but the original lines should all be there too, and look exactly the same as before.

-       All your configuration commands must start with the word “set”.

-       You are not allowed to configure any new IP address.

-       You are not allowed to reboot or restart, totally or partially, any device.


You should accomplish it with two set commands. The solution may require either executing the following at one router only:


<set command #1>

<set command #2>



Or, alternatively, executing on R1:


<set command #1>



... followed by this on R2:



<set command #2>



To solve this challenge submit the two set commands and on which router they are configured.



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.



Configure at R1:

juniper@R1# set routing-instances myVR interface lo0.1

juniper@R1# set interfaces lo0 unit 1 family inet


Why? When a routing instance does not have a loopback unit assigned, its inbound control traffic is processed by the master instance’s loopback unit lo0.0. This was initially filtering out the ICMP echo replies coming from R2.

Note that is just an example, you can use any valid IP address as long as it does not overlap with the network.





Julie Wider
Advocacy Manager
Twitter: @JNetCommunity & @jawider