Router-on-a-Stick practice labs

Scaling to Three VLANs: Adding a Department

Extend a working two-VLAN router-on-a-stick design to a third VLAN (Guest) without breaking Sales and Engineering. Add one router subinterface, one switch VLAN + access port, and update the switch trunk’s allowed-VLAN list safely using 'add' so existing VLANs remain transported.

Router-on-a-Stick Fundamentals: Two VLANs, One Trunk

Configure inter-VLAN routing using router-on-a-stick with one router, one Layer-2 switch, and two hosts. Build VLAN 10 and VLAN 20, trunk the router uplink, create subinterfaces for each VLAN, and verify that hosts can now reach each other across VLANs.

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

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.

dot1Q Subinterfaces: The Router Side

Practice creating 802.1Q subinterfaces on a single router uplink to deliver inter-VLAN routing using router-on-a-stick. The Layer-2 switch is already fully configured with VLAN 10 and VLAN 20, access ports for two hosts, and a working 802.1Q trunk to the router. Your job: leave the router's physical Ethernet0/0 unnumbered and add exactly two subinterfaces with the correct encapsulation tags and gateway IPs so hosts can reach their gateways and each other.

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

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.

Multi-Dept Campus Inter-VLAN with Router-on-a-Stick

Design and implement a three-department campus edge using a single router-on-a-stick to provide inter-VLAN routing for Sales (VLAN 10), Engineering (VLAN 20), and Servers (VLAN 30). Map the addressing plan directly to router subinterfaces and build an 802.1Q trunk on the access switch. Verify end-to-end reachability and troubleshoot an allow-list drift scenario.

Router-on-a-Stick Troubleshooting Capstone

Advanced CCNA capstone: diagnose and repair a fully-broken three-VLAN router-on-a-stick deployment. One iol-xe router uplinks by 802.1Q trunk to a pure layer-2 ioll2-xe switch, with three alpine PCs on their own access VLANs (10 Sales, 20 Voice, 30 CCTV); after a recent switch and router change, inter-VLAN connectivity is broken or intermittent across all three VLANs. Trace VLAN intent end-to-end from each host through the trunk to the router's subinterfaces, repair whatever faults you find, and verify with end-host pings/traceroutes and IOS show commands.

Diagnosing a Broken Router-on-a-Stick

Advanced CCNA troubleshooting lab on a router-on-a-stick design. VLAN 10 users can reach their gateway and other hosts, but VLAN 20 users cannot reach their gateway or any resources in VLAN 10. Methodically trace L2/L3 intent end-to-end - from the access ports through the trunks up to the router subinterfaces - to isolate the first-hop failure and implement fixes that restore inter-VLAN routing while maintaining enterprise trunk hardening and clean configurations.

Lab 7: Inter-VLAN Verification Discipline

Build and verify a three-VLAN router-on-a-stick design: one IOS router provides inter-VLAN routing via 802.1Q subinterfaces to a single Layer-2 access switch, with three Alpine hosts in VLANs 10, 20, and 30. The starter environment does not yet forward traffic correctly between all three VLANs, so you will apply a disciplined router-switch-host verification method to diagnose and fix the problem, then briefly break and restore one VLAN's connectivity before finishing with an enterprise-clean, hardened trunk.

Selective Inter-VLAN Reachability: Guest Isolation

Build a router-on-a-stick design with three VLANs (SALES, HR, GUEST) on a single router and single access switch, then enforce guest isolation using a single extended ACL applied inbound on the Guest subinterface. SALES and HR can reach each other; GUEST can reach only its default gateway and is blocked from internal subnets. The lab focuses on correct 802.1Q tagging, trunking, access port assignments, ACL placement/order, and end-host verification.

CCNA Foundations: L2 Day 7 — VLANs, Trunks & Port Security

Deploy VLANs, hardened 802.1Q trunks, router-on-a-stick inter-VLAN routing, and sticky port security in a compact branch topology. Verify from real hosts and troubleshoot common misconfigurations.

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CCNA: VLAN DB & Trunk Allow-List Drift Recovery

Hands-on CCNA VLAN lab: build VLANs with names, assign access ports, harden and verify 802.1Q trunks, and troubleshoot a broken allow-list that prevents a VLAN from traversing the SW1–SW2 trunk. Includes router-on-a-stick gateways, management VLAN, and end-host validation.