Junos Cup 2014
Junos Cup 2014

Tournament 2: England Challenge & Solution: The Reverse Engineering Saga, Episode 2 - The Broken IGP

[ Edited ]
‎06-19-2014 07:25 AM

You are a Senior Network Engineer that just joined a company desperately in search for an experienced network engineer with deep experience on IP/MPLS networks.

 

On your first day at the company, your boss calls you in for an urgent meeting. He said that he fired the previous engineer responsible for managing the network and just before that person left the company, he deleted all documentation and also introduced a few problems in the network that are affecting the customers of your company that use its network services.

 

The angriest customer is also the one that generates 40% of your company revenue, who has set a very aggressive deadline for your company to fix the problem. If the problem is not solved on time, that key customer will find another supplier to buy network services.

 

When you start to look in the network, you find that the previous engineer also modified the access classes of the users, restricting what commands you are able to execute in the routers.

 

The Reverse Engineering Saga contains four episodes, one previous to the Junos Cup, and the three in the Junos Cup itself: England, Chile, Croatia. 

 

Country Flag: England

 

Author: Diogo Montagner

 

Title: The Reverse Engineering Saga, Episode 2 – The Broken IGP

 

Type: Service Provider

 

Difficulty: Medium (1 point).

 

Technical Description: Solve an IGP problem and precisely gauge its impact.

 

Topology:

10-England-Topology.jpg

Challenge Instructions:

For this challenge, you need to start the topology called: “England – The Reverse Engineering Saga, Episode 2 – The Broken IGP”.

                                                    

You must find a problem in the IGP, and describe its consequence.

 

The traceoptions files result from the following configuration:

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

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

 

In order to describe the impact, state what ping commands are expected to fail, in the format:

 

juniper@[router]> ping [ip]

 

List all the combinations (router, IP), where:

 

-       [router] can be R1, R2, R3, R4 and R5

-       [ip] can be any IP address configured on any of the routers above

 

To solve this challenge  briefly describe the IGP problem, explain its impact, and list all the combinations of (router, IP).

 

TIP: There are 20 pairs in total.

 

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.

 

OFFICIAL SOLUTION:

The problem is that the L2 backbone is not contiguous:

Furthermore, the lo0.0 addresses of R3, R4, and R5 are not advertised in L1.

So the pair list is:

(R1, 10.1.1.21)

(R1, 10.1.1.22)

(R1, 10.1.1.25)

(R1, 10.1.1.26)

(R1, 10.255.255.3)

(R1, 10.255.255.4)

(R1, 10.255.255.5)

(R2, 10.1.1.21)

(R2, 10.1.1.22)

(R2, 10.1.1.25)

(R2, 10.1.1.26)

(R2, 10.255.255.3)

(R2, 10.255.255.4)

(R2, 10.255.255.5)

(R3, 10.1.1.5)

(R3, 10.1.1.6)

(R4, 10.1.1.5)

(R4, 10.1.1.6)

(R5, 10.1.1.5)

(R5, 10.1.1.6)

 

Julie Wider
Advocacy Manager
Twitter: @JNetCommunity & @jawider