configuring-network-segmentation-with-vlans

# 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 ## Workflow ### Step 1: Design the VLAN Architecture ``` # Define VLANs based on security zones and function VLAN Plan: VLAN 10 - CORPORATE (10.10.10.0/24) - Employee workstations VLAN 20 - SERVERS (10.10.20.0/24) - Internal servers VLAN 30 - DMZ (10.10.30.0/24) - Internet-facing servers ...