VLANs Made Sense When I Stopped Thinking of Them as Extra Networks
A VLAN is first a Layer 2 boundary. IP subnets often map to VLANs, but keeping those two concepts separate makes switching and routing much easier to reason about.
VLAN
When One VLAN Would Not Cross the Trunk
A trunk can be up while one VLAN is still broken. That lab pushed me to verify allowed VLANs and operational state instead of assuming the link was simply good or bad.
Trunk Ports: The Part of VLANs I Initially Misunderstood
A trunk does not merge VLANs. It preserves multiple Layer 2 domains across one physical link by carrying VLAN identity with the frame.