What a Switch Actually Learns from a MAC Address
A switch learns from source MAC addresses, not destination addresses. Watching the table populate makes unknown unicast, flooding and forwarding much easier to reason about.
switching
Spanning Tree Stopped Looking Weird Once I Built a Loop on Purpose
STP made more sense after I created the failure it is designed to prevent: a Layer 2 loop with no TTL to save the network.
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.