Native VLAN on a Router-on-a-Stick Trunk

Bundle lab · $29.99

Build and verify inter-VLAN routing using router-on-a-stick with a native (untagged) VLAN on the trunk. Configure one router (subinterfaces only), one Layer-2 access switch (VLANs, access ports, and a single 802.1Q trunk), and two end hosts in different VLANs. The management VLAN 99 rides untagged as the trunk's native VLAN, so the router subinterface must use 'encapsulation dot1Q 99 native' and the switch trunk must match 'switchport trunk native vlan 99'. Verify from Linux hosts and IOS 'show' commands, then practice troubleshooting common native-VLAN faults.

Learning objectives

• Configure router-on-a-stick subinterfaces with correct 802.1Q VLAN tags and the native keyword for the management VLAN.
• Create VLANs on a Layer-2 switch, assign access ports, and build a matching 802.1Q trunk with the correct native VLAN.
• Validate end-to-end reachability from hosts, including cross-VLAN ping and traceroute via the router subinterface.
• Identify and correct native VLAN mismatches and missing VLANs on trunks.

Troubleshooting focus

• Diagnose and resolve the introduced fault: Trunk allow-lists, native VLAN alignment, and host VLAN assignment.
• Verify every link's interface status and IP addressing (`show ip interface brief`) and correct any interface that is down or misaddressed.
• Confirm each device's running configuration matches the lab objective, and bring any interface, route, or service that is not in its expected state back to health.
• Trace end-to-end reachability with ping/traceroute and isolate the first hop where forwarding fails.