VLANs provide logical network segmentation without requiring separate physical switches for each network segment. By isolating broadcast domains, VLANs improve both security and performance in enterprise networks.
VLAN Design and Trunk Configuration
A well-designed VLAN architecture separates traffic by function: management, production, development, guest, and DMZ networks each on their own VLAN. This isolation prevents lateral movement in the event of a security breach and contains broadcast traffic.
Trunk ports carry traffic for multiple VLANs between switches using 802.1Q tagging. Configure native VLANs carefully and avoid using VLAN 1 for production traffic, as it is the default and often targeted in VLAN hopping attacks.
Inter-VLAN routing requires a Layer 3 switch or router. Implement access control lists at the routing layer to control which VLANs can communicate with each other, enforcing the principle of least privilege at the network level.