Junos Cup 2014
Junos Cup 2014

Tournament 3: Chile Challenge & Solution: The Reverse Engineering Saga, Episode 3 – The Strange BGP

[ Edited ]
‎06-26-2014 07:09 AM

Country Flag: Chile

 

Author: Diogo Montagner

 

Title: The Reverse Engineering Saga, Episode 3 – The Strange BGP

 

Type: Service Provider

 

Difficulty: Medium (1 point).

 

Technical Description: Figure out two different BGP issues. You need to figure out both in order to score 1 point.

 

Topology:

Chile-Topology

 

Challenge Instructions:

For this challenge, you need to start the topology called: “CHILE – The Reverse Engineering Saga, Episode 3 – The Strange BGP”.

 

As was the case with previous Episodes of this saga (ENGLAND, etc.) , your Junos user has very few privileges. This time you can can clear protocol sessions, launch ping, or inspect log and traceoptions files.

 

The relevant traceoptions files result from the following configuration:

-       At hierarchy level [edit routing-options] or below: RT.log and RSLV.log

-       At hierarchy level [edit protocols] or below: OSPF.log, BGP.log, and ISIS.log

 

This challenge is built on top of the topology of Episode 2 (England - The Broken IGP), except that now the IGP is not broken anymore. Indeed, now there is only IS-IS L1 across all the links and interfaces, including the loopbacks.

 

To solve this challenge, briefly describe the two different BGP issues in this topology. One is more straightforward to find than the other.

 

TIP: Not all the BGP issues prevent sessions from being Established.

 

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, 1st of July 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.

 

OFFICIAL SOLUTION:

 

Issue #1: R5 has a wrong AS number configured (different from the other IBGP peers), and therefore it cannot establish any BGP session successfully.

 

Issue #2: R1 only tries to negotiate family inet unicast (AFI=1, SAFI=1) with R3. On the other hand, R3 tries to negotiate family inet unicast (AFI=1, SAFI=1), family inet-vpn unicast (AFI=1, SAFI=128) and family inet6 unicast (AFI=2, SAFI=1). This is due to an incomplete BGP group configuration at R1.

 

Julie Wider
Advocacy Manager
Twitter: @JNetCommunity & @jawider