Configuring Network Segmentation with VLANs

When to Use

• Segmenting an enterprise network into isolated security zones (corporate, servers, DMZ, guest, IoT)
• Meeting compliance requirements (PCI-DSS, HIPAA, SOC 2) that mandate network isolation for sensitive data
• Reducing blast radius of security incidents by preventing lateral movement between network segments
• Isolating high-risk devices (IoT, BYOD, legacy systems) from critical infrastructure
• Implementing defense-in-depth by combining VLANs with firewall rules and access control lists

Do not use VLANs as the sole security control without Layer 3 filtering, for isolating networks that require air-gapping, or without proper switch hardening against VLAN hopping attacks.

Prerequisites

• Managed switches supporting 802.1Q VLAN trunking (Cisco Catalyst, HP Aruba, Juniper EX, etc.)
• Layer 3 switch or firewall for inter-VLAN routing and access control
• Network design document specifying VLAN assignments, IP subnets, and traffic flow requirements
• Console or SSH access to switches with privileged configuration mode
• Understanding of 802.1Q trunking, STP, and inter-VLAN routing concepts