Junos Cup 2014
Junos Cup 2014

Tournament 1: Switzerland Challenge & Solution - Aggregated Ethernet Failover

[ Edited ]
‎06-12-2014 07:50 AM

Country Flag associated with this challenge: Switzerland


Author: Tim Hoffman


Title: Aggregated Ethernet Failover


Type: Enterprise


Difficulty: Medium (1 point).


Technical Description: Configure R1 and R2 to achieve the following behavior: if an interface is deactivated at R2, the ping between loopbacks automatically recovers.




Challenge Instructions:

For this challenge, you need to start the topology called: “SWITZERLAND – Aggregated Ethernet failover”.


When you work on this challenge, leave a ping command running from R1 to R2 all the time:


juniper@R1> ping source rapid count 1000000000

PING ( 56 data bytes



There are two routers connected together by two links. The links are bound together into an aggregated ethernet for resiliency.


Your task is to ensure that in the event that there is a failure of one of the member links (not involving a physical link down), traffic fails over to the other link within five seconds.


You can simulate a link failure by executing the following configuration sequence at R2:



deactivate interfaces ge-0/0/0


/* Wait until your ICMP resumes working (must happen within 5secs) */

activate interfaces ge-0/0/0 disable

commit and-quit


Your answer must meet the following conditions:


- You are not allowed to configure LACP or Ethernet OAM.

- You may issue only a single set command per router.

- The configure/edit and commit commands are needed but not counted towards the solution.


To solve this challenge submit the configuration change for both R1 and R2.


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)

Some additional notes:

  • Feel free to participate in as many challenges as you like, they are open to everyone and the more you participate the better chance of winning!
  • Green Planet Rules: please start one topology at a time, do not run several topologies in parallel and don't forget to stop your active topology when not in use
  • 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.



Junos 13.3 introduces a new functionality called Micro BFD for LAG: http://www.juniper.net/techpubs/en_US/junos13.3/topics/concept/bfd-for-lag-overview.html.


The solution is:


juniper@R1# set interfaces ae0 aggregated-ether-options bfd-liveness-detection multiplier 3 minimum-interval 100 local-address neighbor 


juniper@R2# set interfaces ae0 aggregated-ether-options bfd-liveness-detection multiplier 3 minimum-interval 100 local-address neighbor    


NOTE: BFD is an event-driven protocol. If you configure BFD when the link is down, you will see no effect. You need to bring the link down after BFD is already configured, in order to see the feature in action.



Julie Wider
Advocacy Manager
Twitter: @JNetCommunity & @jawider