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.
Ethernet
My First Packet Tracer Lab: Two PCs, One Switch, No Magic
A two-PC switch lab is simple enough to expose the actual sequence behind a successful ping: addressing, ARP, MAC learning and frame forwarding.
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.
Building a Small Home Lab from an Old PC and a Cheap Switch
A useful home lab does not need enterprise hardware. A spare PC, a small switch and a few isolated network experiments are enough to learn a lot about real interfaces, routes and services.