Virtual LANs allow network administrators to segment a physical network into multiple logical broadcast domains without additional hardware. Proper VLAN design improves security, reduces broadcast traffic, and simplifies network management in environments of any size.
Trunk Ports and Access Ports
Access ports carry traffic for a single VLAN and connect to end devices like workstations and servers. Trunk ports carry traffic for multiple VLANs using 802.1Q tagging and connect switches to each other or to routers for inter-VLAN routing. Misconfigured trunk ports are a common source of security vulnerabilities, so always explicitly define allowed VLANs on trunk links.
Inter-VLAN routing can be accomplished using a router with sub-interfaces (router-on-a-stick) or a Layer 3 switch. For environments with significant inter-VLAN traffic, a Layer 3 switch provides wire-speed routing and is the preferred approach. Apply access control lists at the Layer 3 boundary to enforce security policies between VLANs.
Document your VLAN assignments in a central location and use a consistent numbering scheme. Reserve VLAN 1 for native traffic only, assign management VLANs in a dedicated range, and group similar functions together. This structured approach simplifies troubleshooting and onboarding of new network team members.