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Train like a
network engineer.

Router configurations, not multiple-choice questions. Work through network incidents in your browser. Inspect routes, change router configurations, and check whether your repair restores service.

Browse 240 challenges

10 free labs No account No install or credit card

Lab 001Static routing · Easy
Incident brief

The branch cannot reach the service network.

Find the failure. Restore connectivity without changing the topology.

Network topology3 devices 2 links

The unreachable branch — network topologyR1: Client edge. R2: Transit core. R3: Service edge. R1 connects to R2. R2 connects to R3. Connections show physical links, not service health.R1 ↔ R2 · 10.41.12.0/30R2 ↔ R3 · 10.41.23.0/30R1Client edgeR1 · Client edgeR2Transit coreR2 · Transit coreR3Service edgeR3 · Service edge
Physical links · Service health not shown
R1# traceroute 10.41.30.10

1  R1  NoRoute
Not delivered: no route at R1

Example forwarding trace. The live lab accepts your commands.

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Start with a free lab

Choose an incident. Read the brief before you enter the network.

All 240 challenges
  1. Routing

    The unreachable branch

    Traffic stops at the branch router. Find the forwarding failure and restore access to the service network.

    Easy 8 min Free
    Open lab
  2. OSPF

    A neighbor gone quiet

    The client network has lost access to the data center. Check the OSPF neighbors and routing tables.

    Medium 25 min Free
    Open lab
  3. BGP

    The silent peering

    An edge router is no longer learning a service route. Inspect the BGP session and restore the path.

    Medium 25 min Free
    Open lab

Study paths group labs by skill and track your progress.

View study paths

Study paths

Work through a sequence of labs focused on the skills you want to build.

27 labs

Network engineer foundations

Build a repeatable incident-response routine.

29 labs

Routing interview practice

Explain why the route is missing, not just how to add it.

25 labs

Safe network troubleshooting

Restore service while preserving access controls.

Choose a path in your workspace to track your progress.

Open study paths

What you do in a lab

You work on router configurations, not multiple-choice questions.

  1. 01

    Inspect the network

    Read the topology and use familiar commands to investigate routes, neighbors, and packet paths.

    show ip route
  2. 02

    Make a repair

    Change configuration through the terminal or editor. Test the affected service and check for regressions.

    configure terminal
  3. 03

    Submit for grading

    Your repair is tested against the network’s requirements. Review what passed, what failed, and your technical score.

    See the lab guide

Network correctness is verified by the simulator, not AI. Basic scores and two guided hints are free; worked solutions and reference configurations require Pro.

Interview practice

Practice under a time limit.

Try the free 15-minute rehearsal with hints switched off. Review the instructions first; the clock starts only when you choose to begin.

Review interview practice
Pro

The full library, with worked solutions.

Get all 240 incidents, reference configurations, and multi-incident rehearsals. Choose $19 billed monthly or $149 billed annually.

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