Native VLAN & Trunk Mismatch: Detection and Recovery

Bundle lab · $29.99

Configure VLANs and 802.1Q trunks across two access switches with a router-on-a-stick gateway. Intentionally misconfigure the native VLAN and trunk allow-list to observe loss of intra-VLAN connectivity, detect the mismatch using switch warnings and show commands, and then remediate to restore user reachability. Validates VLAN segmentation, trunking symmetry, and troubleshooting skills for CCNA candidates.

Learning objectives

• Create VLANs for users and management and assign access ports
• Build and harden 802.1Q trunks with an explicit allowed VLAN list and a non-default native VLAN
• Detect native VLAN mismatches using syslog/CDP warnings and show commands
• Identify and correct missing VLANs on trunk allow-lists
• Validate intra-VLAN reachability end-to-end and document the fix

Troubleshooting focus

• 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.