implementing-purdue-model-network-segmentation

# Implementing Purdue Model Network Segmentation ## When to Use - When designing or retrofitting network architecture for an ICS/SCADA environment - When implementing IEC 62443 zone and conduit requirements in a brownfield plant - When creating the IT/OT DMZ (Level 3.5) to control data flow between enterprise and control networks - When remediating audit findings about flat OT networks or direct IT-to-OT connectivity - When segmenting a converged IT/OT network after an acquisition or merger **Do not use** for micro-segmentation within a single Purdue level (see implementing-zone-conduit-model-for-ics), for cloud-native environments without traditional ICS networks, or for network segmentation in purely IT environments. ## Prerequisites - Complete OT asset inventory with Purdue level classification for each device - Network architecture diagram showing current topology, VLANs, and firewall placements - Industrial firewalls capable of deep packet inspection for OT protocols (Palo Alto, Fortinet, Cisco) - Understanding of required data flows between Purdue levels (historian replication, remote access, patch distribution) - Change management approval from plant operations for network modifications ## Workflow ### Step 1: Map Current Architecture to Purdue Levels Classify all network assets and data flows according to the Purdue Model hierarchy. ```python #!/usr/bin/env python3 """Purdue Model Network Segmentation Planner. Maps existing OT/IT network assets to Purdue Mod...