How switches forward frames, VLANs segment Layer 2 domains, trunks carry tagged traffic, and loop prevention protects switched networks.
A switch forwards frames within a Layer 2 domain. VLANs create separate Layer 2 and broadcast boundaries on shared switching infrastructure; traffic between VLANs requires Layer 3 routing.
| Element | Role |
|---|---|
| Access port | Connects one endpoint VLAN |
| Trunk port | Carries traffic for multiple VLANs between compatible devices |
| VLAN | Logical Layer 2 segmentation boundary |
| STP | Prevents forwarding loops in redundant switched paths |
| Inter-VLAN routing | Routes traffic between VLANs |
Verify VLAN membership, trunk allowance, tagging expectations, and loop-prevention state before treating a local switching failure as a DNS or routing problem.