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implementing-network-segmentation-for-ot

Designs and validates Purdue Model network segmentation for OT environments using VLANs and industrial firewalls.

954|172|Updated Mar 13, 2026
Search Tags:#VLAN#iec 62443#network segmentation#ICS#purdue model#OT security#industrial firewall
One-click install
npx skills add https://github.com/xalgord/xalgorix --skill implementing-network-segmentation-for-ot
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: implementing-network-segmentation-for-ot
Source: https://github.com/xalgord/xalgorix/tree/main/internal/tools/skills/data/ot-ics-security/implementing-network-segmentation-for-ot
Command: npx skills add https://github.com/xalgord/xalgorix --skill implementing-network-segmentation-for-ot

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

Flat OT networks without segmentation allow threats to move freely between enterprise IT and industrial control systems. This Skill designs a Purdue Model-based segmentation architecture from real traffic baselines, generates firewall rules and VLAN configurations, and validates that zone isolation works without disrupting operations.

Core Features & Use Cases

  • Segmentation Design from Traffic Baselines: Parses passive monitoring baseline JSON to generate VLAN assignments per Purdue level, firewall allow rules from observed flows, DPI profiles for Modbus/EtherNet-IP/OPC UA/S7/DNP3, and a four-phase migration plan with rollback steps.
  • Industrial Switch Hardening: Provides Cisco IE switch configuration for VLANs, port security with MAC binding, storm control, trunk setup, and unused-port quarantine.
  • Post-Deployment Validation: Runs TCP connectivity tests to confirm enterprise-to-PLC traffic is blocked, operations read polls succeed, and SIS is unreachable from the BPCS.
  • Use Case: After an IEC 62443-3-2 risk assessment reveals a flat network, use this Skill to produce a zone/conduit design, configure OT-aware firewalls in monitor-then-enforce mode, and verify segmentation during a maintenance window.

Quick Start

Use this skill to design a Purdue Model segmentation plan from my traffic baseline file baseline.json and generate the VLAN, firewall rule, and validation test outputs.

Frequently Asked Questions about implementing-network-segmentation-for-ot

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I implement network segmentation in an OT environment?▼

Start with 2-4 weeks of passive traffic baseline capture, then design VLANs aligned to Purdue levels and generate firewall rules from observed legitimate flows. Deploy in phases—DMZ first, then L3/L2 separation, field device isolation, and SIS isolation—using monitor mode before enforcement.

What is the Purdue Model for ICS network segmentation?▼

The Purdue Model divides industrial networks into levels: Level 0-1 field devices and PLCs, Level 2 supervisory HMIs, Level 3 site operations, Level 3.5 DMZ, and Level 4 enterprise IT. Segmentation places firewalls between levels so cross-zone traffic is inspected and unauthorized flows are denied by default.

Which firewalls support industrial protocol deep packet inspection?▼

The Skill references Cisco ISA-3000, Fortinet FortiGate Rugged Series, and Palo Alto with OT Security for DPI on Modbus, DNP3, EtherNet/IP, OPC UA, and S7comm. DPI profiles can enforce read-only access by blocking Modbus write function codes from Level 3.

Why does OT segmentation break legitimate traffic after cutover?▼

Cutover failures usually come from an incomplete traffic baseline that misses infrequent flows like quarterly batch reports or vendor polls. Capture 2-4 weeks spanning all operating modes and run firewalls in monitor mode for a week before enforcing rules.

How do I validate OT network segmentation without disrupting operations?▼

Validate during a maintenance window using TCP connect tests only—never write or restart commands against live controllers. Confirm enterprise-to-PLC ports 502/44818/102 are blocked, operations read polls succeed, and SIS is unreachable from the BPCS.

When should I not use this OT segmentation approach?▼

Do not use it for IT-only microsegmentation without OT components, or for initial zone design before any traffic analysis exists. Complete an OT network security assessment and traffic baseline first so firewall rules reflect real communication patterns.

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