A Policy-Correct Multi-VLAN Trunk

Bundle lab · $29.99

Build a single 802.1Q trunk between two Layer-2 switches that correctly carries three VLANs with an explicit allow-list and a dedicated non-default native VLAN. Place hosts in Users (VLAN 10) across both switches and a server in Servers (VLAN 20). Verify that the trunk allows VLANs 10, 20, and 99, that the native VLAN matches on both ends, and that same-VLAN hosts communicate across the trunk. Then intentionally break and restore the configuration to practice troubleshooting trunk allow-lists, native VLAN alignment, and host VLAN placement.

Learning objectives

• Create VLANs and map access ports to the correct VLANs on Layer-2 switches
• Configure a static 802.1Q trunk with an explicit allowed VLAN list and a non-default native VLAN
• Verify trunk status, allowed VLANs, and native VLAN symmetry using show interfaces trunk
• Validate end-host placement and intra-VLAN connectivity across a trunk
• Troubleshoot common trunk issues: omitted VLANs on allow-lists, native VLAN mismatches, and wrong access VLANs

Troubleshooting focus

• A native VLAN mismatch causes unexpected untagged/Native traffic behavior and warnings
• A required VLAN omitted from the trunk allow-list breaks cross-switch reachability for that VLAN
• An access port assigned to the wrong VLAN strands a host in the wrong broadcast domain