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VLANs, Trunking & Spanning Tree

A distribution switch, two access switches and four hosts in VLANs 10 and 20. PC1 can't reach PC2 or its gateway: work through the trunks, the native VLAN and spanning tree.

Download .unlNo lab server? Practise it in your browser
The lab as it opens in PNETLab, with the symptom, objectives and investigation checklist on the canvas.

What you'll practise

  • Configure 802.1Q trunks and verify dot1q encapsulation
  • Identify and fix a native VLAN mismatch across switch trunks
  • Verify VLAN creation and access port assignments (VLAN 10 and 20)
  • Inspect spanning tree root bridge election and port states
  • Verify inter-VLAN routing and host reachability across all switches

Set it up

  1. 1

    Have the node image ready

    Images are not included. The file expects your own licensed copy of:

    • i86bi_Linux-L2-Adventerprisek9-ms.SSA.high_iron_20190423.bin

    If your copy has a different name, open each node's Edit dialog after importing and pick your image from the list.

  2. 2

    Copy it to the server and fix permissions

    Replace <your-server> with the IP address or hostname of your EVE-NG or PNETLab server.

    $ scp vlans-trunking-spanning-tree-lab.unl root@<your-server>:/opt/unetlab/labs/
# then, logged in to the server:
$ /opt/unetlab/wrappers/unl_wrapper -a fixpermissions
  3. 3

    Open it and start the nodes

    The canvas notes list the objectives, and the workbook walks through the fix.

Inside the lab

The real lab topology: one distribution switch, two access switches, four hosts.
Real console output captured live: SW-DIST logs the exact native VLAN mismatch against SW-ACC1's trunk port, repeating on every CDP cycle.
After the fix: PC1 reaches PC2 across the switch block, captured live from PC1's own console.

Free to use and share under CC BY 4.0. Please credit LabFabric with a link to this page.