Junos Cup 2014
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Junos Cup 2014

Tournament 2: Iran Challenge & Solution : LDP with Tagged Traceroute

[ Edited ]
‎06-19-2014 07:29 AM

Country Flag: IRAN

 

Author: Alexander Arseniev

 

Title: LDP with Tagged Traceroute

 

Type: Service Provider

 

Difficulty: High – This challenge has at least two solutions that are conceptually very different, not just variations of the same syntax. The idea here is to award 1 point per solution: 1 solution = 1 point, while 2 solutions = 2 points.

 

Technical Description: Configure a MPLS LDP network using the minimum number of configuration commands, so that traceroute from PE1 to PE2 explicitly shows a labeled path.

 

Topology:

11-Iran-Topology.jpg

 

Challenge Instructions:

For this challenge, you need to start the topology called: IRAN  - LDP with Tagged Traceroute.

 

Configure MPLS using LDP in the network. As a result of your configuration, your submitted traceroute from PE1 through P towards PE2 must show an MPLS label as shown here in boldface font:

 

juniper@PE1> traceroute <dst.IP> no-resolve [source <src.IP>]

traceroute to <dst.ip> (<dst.IP> ), 30 hops max, 40 byte packets

 1  198.51.100.1  14.182 ms  24.871 ms  20.359 ms

     MPLS Label=<label> CoS=0 TTL=1 S=1

 2 <dst.IP>  20.023 ms  30.288 ms  30.277 ms

 

You are free to choose a (<src.IP>, <dst.IP>) pair, as long as they are valid IPv4 addresses configured at (PE1, PE2) respectively. Traceroute must go through P and the traceroute printout must show an IP address belonging to P.

 

Your challenge solution must comply with the following configuration rules:

  • Any IGP can be used.
  • The only valid MPLS label signaling protocol is LDP, and you are not allowed to use static LSPs.
  • No configuration should be deleted, deactivated, or disabled.
  • You can only add new configuration lines. You must not change any existing ones. In other words, if you execute show | compare there should be no lines starting with a minus (-) sign.
  • You are free to use as many configuration commands at P as you wish.
  • You can use a maximum of five set commands at PE1, such as:

 

configure

<set command #1>

<set command #2>

<set command #3>

<set command #4>

<set command #5>

commit

 

  • You can use a maximum of four set commands at PE2.

NOTE: Certain protocols are pre-disabled on ge-0/0/0.0 interfaces on all routers in order to avoid polluting the management subnet.

 

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:

Both solutions A and B share this baseline configuration:

PE1:

set interfaces ge-0/0/1 unit 0 family mpls

set protocols ospf area 0 interface all

set protocols ldp interface all

set interfaces lo0 unit 0 family inet address 198.51.100.250/32

P:

set interfaces ge-0/0/1 unit 0 family mpls

set interfaces ge-0/0/2 unit 0 family mpls

set interfaces lo0 unit 0 family inet address 198.51.100.251/32

set protocols ldp interface all

set protocols ospf area 0 interface all

PE2:

set interfaces ge-0/0/1 unit 0 family mpls

set interfaces lo0 unit 0 family inet address 198.51.100.252/32

set protocols ospf area 0 interface all

set protocols ldp interface all

 

In addition to the baseline configuration, solution A has:

juniper@PE1# set protocols mpls traffic-engineering [ bgp-igp | bgp-igp-both-ribs | mpls-forwarding ]

juniper@PE1# commit and-quit

juniper@PE1> traceroute 198.51.100.252   

traceroute to 198.51.100.252 (198.51.100.252), 30 hops max, 40 byte packets

 1  198.51.100.1 (198.51.100.1)  22.298 ms  19.028 ms  20.408 ms

     MPLS Label=299776 CoS=0 TTL=1 S=1

 2  198.51.100.252 (198.51.100.252)  18.890 ms  19.546 ms  20.083 ms

 

In addition to the baseline configuration, solution B has:

juniper@PE1# set routing-options static route 198.51.100.3/32 next-hop 198.51.100.252 resolve  

juniper@PE1# commit and-quit

juniper@PE1> traceroute 198.51.100.3     

traceroute to 198.51.100.3 (198.51.100.3), 30 hops max, 40 byte packets

 1  198.51.100.1 (198.51.100.1)  23.878 ms  19.505 ms  20.444 ms

     MPLS Label=299776 CoS=0 TTL=1 S=1

 2  198.51.100.3 (198.51.100.3)  30.293 ms  29.694 ms  30.312 ms

 

 

 

Julie Wider
Advocacy Manager
Twitter: @JNetCommunity & @jawider