implementing-iec-62443-security-zones

# Implementing IEC 62443 Security Zones ## When to Use - When designing a greenfield OT network architecture for a new industrial facility - When retrofitting security zones into an existing flat OT network after an assessment finding - When implementing network segmentation to comply with IEC 62443-3-2 certification requirements - When upgrading from basic VLAN segmentation to policy-enforced zone/conduit architecture - When an IT/OT convergence project requires defining security boundaries between enterprise and operational networks **Do not use** for IT-only network segmentation (see implementing-network-microsegmentation), for cloud-native workload segmentation (see securing-kubernetes-on-cloud), or for physical security zone design without a cyber component. ## Prerequisites - Completed OT network security assessment with asset inventory and traffic flow analysis - Understanding of IEC 62443-3-2 zone/conduit design process and the Purdue Reference Model - Industrial firewalls capable of deep packet inspection for OT protocols (Palo Alto with OT Security, Fortinet OT, Cisco ISA-3000) - Network switches supporting VLANs, 802.1Q trunking, and port security - Approval from operations management for network architecture changes during maintenance windows ## Workflow ### Step 1: Perform Zone Partitioning Based on Risk Assessment Partition the IACS into zones based on functional requirements, security requirements, criticality, and consequence of compromise. Each zone c...