Open the lab

[ YOUR LAB FILE ]

Download the starting topology, then work through the lesson in SwitchLab.

Download SwitchLab Lab (.swlab)

  1. Save the .swlab file without renaming its extension.
  2. Open SwitchLab. Import and export controls currently require a desktop-width window. On a smaller screen, Tools → Fit brings the topology into view.
  3. Select Import Sandbox (folder icon), choose the downloaded file, and confirm the device and cable counts below.
  4. Select a device, then choose Open device on desktop or its name in the bottom bar on smaller screens. Select CLI for switches/routers or Desktop → Terminal for PCs. Enter enable only when the prompt ends in >.
  5. Follow this page beside the simulator. Use a free account to export your work. Reimport the original download to restart; export any work you want to keep first.

Prerequisites

  • Complete the focused lessons for the features used in this scenario.
  • For campus policy scenarios, complete VLANs, trunks, IPv4, OSPF and ACL lessons first.

Follow the CCNA study path · Browse all SwitchLab labs

Topology

Restore a Branch after a Failed Change: starting network imported into the SwitchLab sandbox.
Starting topology captured in SwitchLab. Select the image to view it at full size.

4 devices · 3 links

Scenario

A maintenance script changed a static route and disabled the remote user interface. The transit is still up. Recover the branch without replacing the correct host settings or return route.

Objectives

  • Implement or restore the approved network design without breaking required control paths.
  • Verify configuration, end-to-end behavior and completed-network persistence.
  • Produce an operational handoff with evidence and a deterministic reset path.

CCNA blueprint

200-301 v1.1 objectives — this lab covers the following specific skills, not every subtopic in the domain.

  • 1.6 — Apply and verify the scenario’s IPv4 addressing.
  • 3.3 — Repair an IPv4 static route and its forwarding path.

Starting information

  • PC1 uses 10.10.10.0/24 through R1 g0/0=10.10.10.1; PC2 is 10.20.20.20/24 through R2 g0/0=10.20.20.1.
  • The g0/1 transit is 10.0.12.1/30 on R1 and 10.0.12.2/30 on R2. Preserve all cables and router addresses.
HostIPv4 addressMaskGateway
PC110.10.10.10255.255.255.010.10.10.1
PC210.20.20.20255.255.255.010.20.20.1
RouterInterfaceIPv4 addressMask
R1g0/010.10.10.1255.255.255.0
R1g0/110.0.12.1255.255.255.252
R2g0/010.20.20.1255.255.255.0
R2g0/110.0.12.2255.255.255.252
Device / portDevice / port
PC1 / eth0R1 / g0/0
R1 / g0/1R2 / g0/1
PC2 / eth0R2 / g0/0

Tasks

  1. Compare both routers’ interface and route output with the cable/address plan.
  2. Identify the forwarding and destination-interface faults; explain why correcting only one cannot restore the service.
  3. Apply the smallest two repairs, then test each host’s local gateway and both intersite directions.
  4. Save/export/reload and document the fault-to-evidence mapping for the incident handoff.

Useful commands

show ip interface brief
show ip route
show running-config
copy running-config startup-config

Progressive hints

Hint 1

Break the end-to-end path into host settings, local VLAN carriage, gateway reachability, route selection and any access policy.

Hint 2

Use a working control at each layer. Do not remove security controls or add broad routes just to make one ping succeed.

Hint 3

Compare each affected host, interface and route against the approved plan; use the earlier focused lessons for the exact command patterns.

Verification

  • The final network matches every approved addressing, VLAN, routing and policy requirement above.
  • Every required positive path succeeds and every forbidden path remains blocked.
  • Completed export/reload retains the result; reimporting the starter restores the original exercise.

Solution / walkthrough

Show Solution

Use enable only from a > prompt; if already at #, begin with configure terminal.

R1

Use the actually connected peer as next hop.

enable
configure terminal
no ip route 10.20.20.0 255.255.255.0 10.0.12.99
ip route 10.20.20.0 255.255.255.0 10.0.12.2
end
copy running-config startup-config

R2

Restore the destination LAN interface; a correct route cannot deliver to a disabled LAN.

enable
configure terminal
interface g0/0
no shutdown
end
copy running-config startup-config

Run every verification check above after the changes. A saved configuration alone does not prove packet delivery.

Previous lab

Separate Host, Switching and Routing Faults

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