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 the VLAN and trunking progression.
- Understand that redundant Layer 2 paths need loop prevention.
Topology
5 devices · 5 links
Scenario
A replacement access switch was imported with VLAN 10 priority 0. Host traffic still works, but it has displaced the intended distribution root. Restore the design with one targeted change.
Objectives
- Determine the root from operational spanning-tree output.
- Verify explicit bridge priorities and converged host forwarding.
CCNA blueprint
200-301 v1.1 objectives — this lab covers the following specific skills, not every subtopic in the domain.
- 2.5 — Interpret Rapid PVST+ root election, port roles and steady-state redundancy.
Starting information
- SW1 priority 4096 and SW2 priority 8192 are approved. SW3 should use priority 32768.
- The fault concerns path selection and root placement, not total loss of connectivity. Preserve the working VLAN and trunk configuration.
| Host | IPv4 address | Mask | Gateway |
|---|---|---|---|
| PC1 | 192.168.10.10 | 255.255.255.0 | None |
| PC2 | 192.168.10.20 | 255.255.255.0 | None |
| Device / port | Device / port |
|---|---|
| SW1 / g0/7 | SW2 / g0/7 |
| SW1 / g0/8 | SW3 / g0/8 |
| SW2 / g0/8 | SW3 / g0/7 |
| PC1 / eth0 | SW2 / g0/1 |
| PC2 / eth0 | SW3 / g0/1 |
Tasks
- Use spanning-tree output from all switches to identify the current root and why it won.
- Find the one priority that conflicts with the approved plan and repair it.
- Verify SW1 is now root and SW3 is not; confirm the configured priorities on all three devices.
- Repeat host pings, save/export and explain why a ping-only health check missed this incident.
Useful commands
show spanning-tree vlan 10
show running-config
copy running-config startup-configProgressive hints
Hint 1
Check the bridge priority before using MAC addresses to break an election tie.
Hint 2
A working ping proves delivery but does not tell you whether the intended switch is the root.
Hint 3
Use show spanning-tree vlan 10 on each switch; set only the priorities specified in the approved plan.
Verification
- The intended root reports This bridge is the root for its assigned VLAN.
- Configured bridge priorities match the approved primary and backup design.
- Both directions of each department’s traffic succeed after the final restoration.
Solution / walkthrough
Show Solution
Use enable only from a > prompt; if already at #, begin with configure terminal.
SW3
Remove the accidental root preference on SW3; retain both approved distribution-switch priorities.
enable
configure terminal
spanning-tree vlan 10 priority 32768
end
copy running-config startup-configRun every verification check above after the changes. A saved configuration alone does not prove packet delivery.