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
Three switches form a triangle. SW1 is already the intended root for VLAN 10. Document why this redundant topology can forward frames without using every physical path simultaneously.
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
- VLAN 10 priorities are SW1=0, SW2=4096 and SW3=32768. SW1 should be root.
- All interswitch links are trunks carrying VLAN 10. Both host ports are access ports in VLAN 10.
- SwitchLab models the converged spanning tree. Do not infer real convergence timing or BPDU packet-capture behavior from this exercise.
| 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
- Predict the root using the configured priorities, then run
show spanning-tree vlan 10on all three switches. - Identify the root, designated and alternate roles. Match each interface to the cable table; explain why an alternate port can have a live physical cable while it does not forward ordinary traffic for this VLAN.
- Ping between the two PCs, then label SW1 g0/7 with description TO_SW2_ROOT_PATH to make the documented path identifiable.
- Temporarily shut g0/7 on both SW1 and SW2. Inspect the new converged roles and repeat the host pings; restore both interfaces and verify the original design.
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.
SW1
The root election is already correct. Annotate the known root-facing path after verifying the actual roles; do not change priorities simply to obtain connectivity.
enable
configure terminal
interface g0/7
description TO_SW2_ROOT_PATH
end
copy running-config startup-configRun every verification check above after the changes. A saved configuration alone does not prove packet delivery.