Trunk Verification & Diagnosing a Silent VLAN

Bundle lab · $29.99

An advanced CCNA switching lab focused on verifying 802.1Q trunks and diagnosing a silent VLAN after a switch refresh. The topology uses three layer-2 switches (a distribution switch between two access closets) and two Alpine hosts, and users in VLAN 20 at one closet cannot reach their VLAN 20 peers at the other closet across the trunk path. Learners use show interfaces trunk, show interfaces switchport, and show vlan brief to locate the break and restore predictable Layer-2 forwarding without adding any Layer-3 configuration.

Learning objectives

• Configure and verify 802.1Q trunks on layer-2 switches
• Interpret show interfaces trunk, show interfaces switchport, and show vlan brief to locate trunk/VLAN faults
• Align native VLANs and trunk allowed VLAN lists across a multi-switch path
• Validate end-host access VLAN placement and expected same-VLAN isolation/forwarding
• Apply trunk hardening practices (pin the native VLAN to 999, disable trunk renegotiation, keep VLAN 1 off the trunk)

Troubleshooting focus

• Identify a silent VLAN caused by an incomplete trunk allowed VLAN list
• Recognize and remediate a native VLAN mismatch across trunk ends
• Detect a host interface placed in the wrong access VLAN