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JANOG51 NETCON Walkthrough (Level 1-4): Troubleshooting RIP

Combine static routes and RIP redistribution to restore connectivity from Osaka-B, including its loopback interface, to Tokyo-A.

JANOG51 in Fujiyoshida event banner with dates, snow-covered Mount Fuji, and a five-story pagoda
Contents
  1. Topology
  2. Problem statement
  3. Goal
  4. Restrictions
  5. Walkthrough
  6. Issues
  7. Expected solution
  8. Scoring
  9. Configuration steps
  10. Closing thoughts

This post publishes the JANOG51 NETCON level 1-4 walkthrough on behalf of its author, 村久木. Thank you for creating the challenge.

The explanation below is from the challenge author.

Topology

Topology showing Tokyo-A, Osaka-A, and Osaka-B with physical and loopback interface addresses

Problem statement

You are a network engineer at a company with its headquarters in Osaka and a branch office in Tokyo.

Osaka-A’s Ethernet1/1 can communicate with Tokyo-A’s Ethernet1/1, and Osaka-A’s Ethernet1/2 can communicate with Osaka-B’s Ethernet1/1. However, Osaka-B’s Ethernet1/1 cannot communicate with Tokyo-A’s Ethernet1/1.

The Osaka routers use RIP. Connectivity to Tokyo must use a different method. Enable communication from Osaka-B to Tokyo-A.

Goal

Pings from each interface on Osaka-B must succeed to:

  • 200.1.1.1
  • 201.201.11.1
  • 201.201.12.1

Restrictions

  • Do not configure 200.1.1.1/24 as Osaka-B’s default gateway.
  • Do not configure RIP on Tokyo-A.
  • Do not add IP addresses to loopback interfaces.

Walkthrough

Thank you to everyone who participated in JANOG51 NETCON. This was my first time creating a challenge through the program for new challenge authors.

Issues

There are two problems:

  1. Incomplete routing configuration prevents Osaka-B and Tokyo-A from learning routes to each other.
  2. Tokyo-A lacks a route to Osaka-B’s Loopback1, so communication using that source interface fails.

Expected solution

The expected solution combines the following changes:

  • Configure static routes, a route-map, and redistribution of static routes into RIP on Osaka-A.
  • Configure a static route on Tokyo-A.
  • Enable RIP on Osaka-B’s Loopback1.

Scoring

Score Requirement
50% Osaka-B’s Ethernet1/1 can communicate with Tokyo-A
100% Both Ethernet1/1 and Loopback1 on Osaka-B can communicate with Tokyo-A

Configuration steps

On Osaka-A, add static routes to Tokyo-A’s Loopback1 and Loopback2 networks. Use Tokyo-A’s Ethernet1/1 address as the next hop.

Osaka-A#configure terminal
Osaka-A(config)# ip route 201.201.11.0 255.255.255.0 200.1.1.1
Osaka-A(config)# ip route 201.201.12.0 255.255.255.0 200.1.1.1

On Tokyo-A, add the return route to the Osaka networks via Osaka-A’s Ethernet1/1 address.

Tokyo-A#configure terminal
Tokyo-A(config)# ip route 150.100.0.0 255.255.0.0 200.1.1.2

Create a route-map named netcon on Osaka-A. A permit entry without a match condition allows the static routes being redistributed.

Osaka-A#configure terminal
Osaka-A(config)# route-map netcon permit

Redistribute the static routes into the RIP instance used within Osaka.

Osaka-A(config)#router rip 0
Osaka-A(config-router)# address-family ipv4 unicast
Osaka-A(config-router-af)# redistribute static route-map netcon

At this point, Osaka-B’s Ethernet1/1 can reach Tokyo-A, meeting the 50% scoring requirement.

The Osaka routers use rip 0, where 0 is the instance tag. Enable RIP on Osaka-B’s Loopback1 to advertise its route and allow communication from all of Osaka-B’s interfaces.

Osaka-B#configure terminal
Osaka-B(config)# int loopback1
Osaka-B(config-if)# ip router rip 0

Verify connectivity using both the default source and Loopback1.

Osaka-B#ping 200.1.1.1
Osaka-B#ping 201.201.12.1
Osaka-B#ping 201.201.11.1
Osaka-B#ping 200.1.1.1 source-interface loopback1
Osaka-B#ping 201.201.12.1 source-interface loopback1
Osaka-B#ping 201.201.11.1 source-interface loopback1

Closing thoughts

Seeing solutions beyond the expected answer was a valuable learning experience. Thank you to everyone who participated.

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