Open the lab
[ YOUR LAB FILE ]
Download the starting topology, then work through the lesson in SwitchLab.
- Save the .swlab file without renaming its extension.
- Open SwitchLab. Import and export controls currently require a desktop-width window. On a smaller screen, Tools → Fit brings the topology into view.
- Select Import Sandbox (folder icon), choose the downloaded file, and confirm the device and cable counts below.
- 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
enableonly when the prompt ends in >. - 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 Configure Your First IPv4 Static Routes and understand the return path.
- Distinguish configured routes from installed routes and administrative distance from prefix length.
Topology
4 devices · 4 links
Scenario
Two routers have a primary circuit and a backup circuit. Traffic works, but the HQ router prefers the backup because its route has the wrong administrative distance. Repair the preference without losing failover.
Objectives
- Compare configured backup routes with the currently installed forwarding route.
- Use administrative distance to keep a backup dormant while the primary is usable.
- Prove bidirectional failover and restore the normal path.
CCNA blueprint
200-301 v1.1 objectives — this lab covers the following specific skills, not every subtopic in the domain.
- 3.1.a — Identify a static route in the IPv4 routing table.
- 3.1.d — Verify the next-hop address.
- 3.2.b — Compare administrative distance for routes to the same prefix.
- 3.3.d — Configure and verify IPv4 floating static routes during a bilateral circuit shutdown.
Starting information
- Primary circuit: g0/1, 10.0.12.0/30. Its /24 routes have administrative distance 10. Backup circuit: g0/2, 10.0.99.0/30.
- The required backup administrative distance is 200 on both routers. Routing preference is evaluated for the same destination prefix; lower distance is preferred.
- The two local LANs and all interface addresses are correct. Do not change the primary route or use a routing protocol.
- For the outage test, shut g0/1 on both R1 and R2. Verify both routers select the backup and both workstation directions work, then restore g0/1 on both routers before saving.
- Simulator boundary: a one-sided routed-port shutdown does not yet withdraw the peer’s connected route. This exercise models a planned bilateral circuit shutdown; do not interpret it as proof of physical carrier-loss detection or remote failure tracking.
| Host | IPv4 address | Mask | Gateway |
|---|---|---|---|
| PC1 | 10.10.10.10 | 255.255.255.0 | 10.10.10.1 |
| PC2 | 10.20.20.20 | 255.255.255.0 | 10.20.20.1 |
| Router | Interface | IPv4 address | Mask |
|---|---|---|---|
| R1 | g0/0 | 10.10.10.1 | 255.255.255.0 |
| R1 | g0/1 | 10.0.12.1 | 255.255.255.252 |
| R1 | g0/2 | 10.0.99.1 | 255.255.255.252 |
| R2 | g0/0 | 10.20.20.1 | 255.255.255.0 |
| R2 | g0/1 | 10.0.12.2 | 255.255.255.252 |
| R2 | g0/2 | 10.0.99.2 | 255.255.255.252 |
| Device / port | Device / port |
|---|---|
| PC1 / eth0 | R1 / g0/0 |
| R1 / g0/1 | R2 / g0/1 |
| PC2 / eth0 | R2 / g0/0 |
| R1 / g0/2 | R2 / g0/2 |
Tasks
- Read both running configurations and routing tables. Identify which circuit carries the remote /24 on each router; a successful ping alone cannot prove that the intended circuit is preferred.
- Correct R1’s backup administrative distance to 200 without changing either primary route.
- Verify that normal traffic uses 10.0.12.x next hops and that the backup routes remain in the running configurations.
- Shut g0/1 on both R1 and R2 to remove the primary circuit. Inspect the installed remote /24 routes on both routers and test both workstation directions over the backup.
- Re-enable g0/1 on both routers. Verify the primary is preferred again and save the restored state. This tests deterministic path selection, not elapsed convergence time.
Useful commands
show ip interface brief
show ip route
show running-config
ping 10.0.12.2
ip route <network> <mask> <next-hop>
copy running-config startup-configProgressive hints
Hint 1
Compare route entries for exactly the same destination /24. Traffic can succeed over the wrong circuit.
Hint 2
A floating static route needs a larger administrative distance than the preferred route. It need not appear in the forwarding table while the primary is available.
Hint 3
The backup peers are 10.0.99.2 from R1 and 10.0.99.1 from R2. Use distance 200, then verify both the normal and primary-down states.
Verification
- Normal operation installs each remote /24 through 10.0.12.x at distance 10. Both backup routes remain configured at distance 200.
- With R1 g0/1 shut, R1 installs its remote /24 via 10.0.99.2 and R2 via 10.0.99.1 at distance 200.
- Both workstation directions succeed during the outage and after the primary is restored.
- Finish with both g0/1 endpoints enabled and the primary next hops selected again.
Solution / walkthrough
Show Solution
Use enable only from a > prompt; if already at #, begin with configure terminal.
R1
The original backup distance 1 outranks the primary distance 10. Replacing it with distance 200 restores the intended preference while retaining the alternate route.
enable
configure terminal
no ip route 10.20.20.0 255.255.255.0 10.0.99.2
ip route 10.20.20.0 255.255.255.0 10.0.99.2 200
end
copy running-config startup-configRun every verification check above after the changes. A saved configuration alone does not prove packet delivery.