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BeginnerPublished 2026-06-30

Switch Trunk and Access Ports for Router-on-a-Stick

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Configure the Layer-2 switch side of a router-on-a-stick design. A single IOS router already provides inter-VLAN routing on Ethernet0/0.10 (10.0.10.1/24) and Ethernet0/0.20 (10.0.20.1/24). Bring up VLAN transport by creating VLANs on the switch, assigning host access ports, and converting the router-facing link into an 802.1Q trunk that carries VLANs 10 and 20. Validate with show commands on the switch and with cross-VLAN pings from the hosts.

Track
Est. time
30 minutes
Difficulty
Beginner
Topics

Learning objectives

  • Create VLANs on a Layer-2 switch and assign access ports appropriately
  • Configure an 802.1Q trunk toward a router for router-on-a-stick inter-VLAN routing
  • Verify VLAN membership and trunk state with IOS show commands
  • Validate end-to-end inter-VLAN reachability from Linux hosts

Troubleshooting focus

  • ping 10.0.10.1 from PC-A fails: verify Ethernet0/1 is an access port in VLAN 10. Check with show vlan brief.
  • Both hosts reach their own gateways but not each other: confirm Ethernet0/0 is in trunk mode with VLANs 10 and 20 allowed. Check with show interfaces trunk.
  • The trunk looks correct but cross-VLAN traffic still drops: on RTR-BR-EDGE1, show ip interface brief should list Ethernet0/0.10 and Ethernet0/0.20 up/up, each tagging its matching VLAN. Verify only — do not change the router.
  • traceroute 10.0.20.10 from PC-A goes nowhere: check the PC's default route points at its own gateway. A missing default route blocks cross-VLAN testing.

Topology

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Learn VLANs, Trunking & Inter-VLAN RoutingWhat Is a VLAN? VLANs Explained for Beginners

Grade your work

How this lab is graded
  • Build it your way. Where a lab lets you choose a value — a VLAN name, an interface description — grading checks that you configured it, not which name you picked. Names that another line has to reference, like an ACL applied with access-class, are stated in the guide and do have to match.
  • Addresses, modes and protocol keywords are exact. An IP address, a subnet mask, switchport mode trunk, an encapsulation — these carry the meaning of the lab, so they are graded as written in the guide.
  • Grading reads your saved configuration. Export the lab from CML after you have configured it, and make sure anything you set is in the running-config — a change that only exists in a terminal session never reaches the grader.
  • You can submit as many times as you like. Your best score stands, and each attempt tells you which checks passed so you can work the gaps.
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