802.1Q Trunking Troubleshooting Capstone

Bundle lab · $29.99

Advanced CCNA switching capstone centered on restoring end-to-end VLAN 20 transport across three Layer-2 switches using 802.1Q trunks. The starter ships intentionally broken: after a simulated maintenance window, two Alpine hosts in VLAN 20 can no longer reach each other across the inter-switch trunks. Learners diagnose with show interfaces trunk, show interfaces switchport, and show vlan brief, then identify and correct the trunking faults in the right order and verify with host pings.

Learning objectives

• Trace end-to-end VLAN 20 transport across multiple L2 switches and verify trunk state.
• Identify and remediate a DTP mode combination that prevents trunk formation (auto/auto).
• Detect and correct a native VLAN mismatch on a trunk.
• Audit and fix a trunk allowed VLAN list that omits a required VLAN.
• Differentiate host access VLAN correctness from trunk transport failures.

Troubleshooting focus

• Correlate host ping failures to trunk state, native VLAN alignment, and allow-lists.
• Use show interfaces trunk, show interfaces switchport, and show vlan brief to pinpoint where VLAN 20 transport fails.
• Apply a systematic order of operations: form trunks first, align native VLANs, then correct allow-lists.