The Tool Desk
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Choose an OT asset inventory and network monitoring platform by testing it against the equipment, network zones and operating constraints in your plants—not by comparing generic feature lists or protocol counts. Require vendors to show what they can identify on representative legacy devices, explain how they collect the evidence safely, and distinguish observed facts from inferred attributes and unknowns.
Passive monitoring can provide ongoing visibility without sending discovery traffic to monitored equipment, but it cannot reveal every asset or attribute on its own. A dependable inventory may also need approved queries, existing records, logs, configuration data and manual validation.
Start by defining which assets the platform must cover
Write down the sites and network zones in scope, the teams that will use the inventory, and the equipment families that matter. Include PLCs, HMIs, SCADA and DCS components, RTUs, engineering workstations, controllers and network devices, as applicable.
Mark the assets or locations that are serial-only, disconnected, intermittent, segmented, or unable to tolerate active probing. Note critical processes and any site-specific approval or change-control requirements. These details shape what a platform can see and how it can collect data.
#1 Best Overall
- An industrial 30-ch relay module controlled via Ethernet port, adopts Modbus RTU/Modbus TCP protocols, supports PoE power supply, also comes with an ABS rail-mount case. Applicable to Industrial Control, Smart Home, Smart Agriculture, Breeding / Farming
- The Modbus POE ETH Relay 30CH is very easy to use. Due to its fast communication, stability, reliability, and safety, it is an ideal choice for industrial control equipments and/or applications with high communication requirements
- Features flash-on, flash-off function, by passing argument to the command, it is possible to turn on the relay for a while and then close it automatically. Supports DC 7~36V wide range power input and PoE power supply. Supports relay control through MQTT protocol, comes with Alibaba Cloud MQTT application demo
- Onboard Optocoupler isolation, prevent the relay from being interfered by high-voltage circuit. 4 LEDs and Network indicators for indicating the MCU status and signal transceiving status. 4 LEDs and Network indicators for indicating the MCU status and signal transceiving status
- Adopts dedicated relay driver chip, with built-in flyback diode protection, for stronger and more stable driving ability. Reverse-proof circuit, prevent the circuit from being damaged accidentally by incorrect connection. High quality relay, contact rating: ≤10A 250VAC/30VDC
NIST’s 2026 announcement for an ongoing OT asset-management project describes legacy-device limitations, diverse protocols, distributed assets and operational constraints as challenges to inventory completeness. It is a project announcement, not a completed product comparison or an endorsement of a particular platform: NIST NCCoE’s OT asset-management project.
Compare discovery methods—and review their safety separately
Passive monitoring
Passive monitoring analyzes traffic copied from the network, commonly through a switch SPAN, mirror or monitor port. Because it observes copied traffic rather than initiating discovery traffic to the monitored equipment, it can support ongoing visibility without querying fragile devices. Claroty describes this collection pattern in its passive monitoring overview.
Its limits follow from what is visible on the network: quiet, disconnected or otherwise unseen assets may not appear, and observed traffic may not expose every useful device attribute. A passive-only platform should not be assumed to produce a complete inventory in every environment.
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- The Healuck firewall appliance, equipped with n150 processor(4 Cores 4 Threads, up to 3.6GHz, TDP 6W), is compatible with multiple open-source systems, such as OPNsense. It is easy to configure and manage and supports the AES new instruction set
- Storage: Healuck N150 firewall router equipped with 1 x DDR4 SODIMM Max 32GB, 1 x M.2 Key-M 2280/2242 NVMe/SATA Slot (PCIe 3.0 x 1), 1 x MINIPCe slot (supports 4G Module), 1 x SATA 3.0 (7-pin) Slot, and 1 x SIM Card Slot (LTE modem not included)
- Abundant Interfaces – Provides 4 x i226V 2.5GbE LAN ports, 4 x USB 2.0 ports, 2 x USB 3.0 ports, 2 x DB9 RS232 COM ports, 1 x HD interface, 1 x DP interface,HD+DP Dual Dispaly. and 1 x DC 12V interface, suitable for industrial environments or multi-device access
- Industrial-grade design – Fanless cooling, all-metal casing, quiet operation, suitable for long-term stable work
- Versatile applications – Suitable for firewalls (pfSense/OPNsense), software routers, small servers, industrial automation, etc
Queries and other sources
Ask vendors to identify every collection method they propose, including active or “safe” queries, log or API queries, configuration imports and other integrations. For each query, request the protocol, command or request behavior, expected load, possible failure modes, approval controls and pilot plan. Have site engineering and operations staff review the behavior; the label “safe” is not a substitute for site-specific review.
CISA lists active scanning, passive flow monitoring, log queries and API queries as possible asset-discovery methods. Its BOD 23-01 is a 2022 directive for federal civilian agencies, not a universal OT product-selection standard. It also distinguishes non-intrusive asset discovery from vulnerability enumeration, which depends on suitable privileges or client-based methods where technically feasible.
Inventory is not the same as vulnerability detail
A platform finding a device does not mean it can enumerate that device’s installed software, configuration or vulnerabilities. Ask what evidence supports each security finding: observed network data, a safe query, credentials, an endpoint agent or an external integration. Treat discovery coverage and vulnerability-enumeration coverage as separate evaluation results.
Rank #3
- GOLD SECURITY PACK INCLUDED (1 YEAR): Anti-malware, sandboxing, IPS 2,500 Mbps, web filtering, DNS/IP/URL reputation, app patrol, AI SecuPilot, full UTM active from day one for up to 100 users
- OFFLINE-CAPABLE SETUP AND UPDATES: Configure via Nebula portal wizard; update firmware offline via FTP on the local network, while the web interface remains fully accessible without internet after each update
- RACK-MOUNT FANLESS DESIGN: with SPI 6,500 Mbps firewall throughput, 2,500 Mbps IPS, 1,200 Mbps VPN, the firewall supports up to 100 users, 600,000 concurrent sessions, 100 IPSec tunnels, 50 SSL VPN users, and 32 VLANs
- MULTI-GIG FLEXIBLE PORTS: 6 x 1G plus 2 x 2.5G RJ-45 ports assignable as WAN or LAN, WAN load balancing, active-backup failover, 32 VLAN interfaces, Link Aggregation, and Device HA
- NEBULA MANAGEMENT AND VPN: Centralized policy control, threat monitoring, and SD-VPN orchestration; supporting IKEv2/IPSec, SSL, Tailscale VPN, 100 IPSec tunnels, 50 SSL VPN users, and up to 40 managed APs
Test identification on equipment that represents your plant
Ask each vendor to map supported protocols and identification fields to the actual equipment and protocol variants in your inventory. Select a proof-of-capability set that includes older and newer controllers, HMIs, network equipment and less common protocols. A general protocol count does not show whether a specific model or variant will be identified.
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For each test asset, record whether the platform identifies its manufacturer, model, firmware, role and communication relationships, and how confident it is. Require a clear account of what is observed, what is inferred and what remains unknown when evidence is incomplete. Compare those results with plant records and review discrepancies with staff who know the equipment.
Dragos describes limited device telemetry, proprietary ICS protocols and segmented architectures as legacy OT visibility challenges in its network security monitoring overview. That vendor description helps frame questions for a trial; it is not independent evidence of comparative product performance.
Rank #4
- ✔ 4 Gigabit Ethernet Data Ports: Features four 10/100/1000 Mbps RJ45 Gigabit Ethernet interfaces with bypass capability for secure industrial network connectivity and segmentation.
- ✔ Dedicated Management Interface: Includes a dedicated 10/100/1000 Mbps management port for simplified administration, monitoring, and secure device management.
- ✔ Enterprise-Class Security: Provides advanced firewall, VPN, network segmentation, and industrial threat protection for manufacturing, utilities, transportation, and critical infrastructure.
- ✔ High Reliability: Supports dual DC power inputs, alarm I/O, hardware security technologies, and high availability features for continuous industrial operation.
- ✔ Industrial Security Appliance: Designed to protect industrial control systems (ICS) and operational technology (OT) networks with enterprise-grade firewall and security capabilities.
Check whether the proposed architecture fits every site
Ask where sensors will be placed, how mirrored traffic reaches them, how remote sites connect, and what happens to management and visibility during a WAN outage. Document bandwidth, segmentation, cloud dependencies and whether the design can operate locally if your requirements call for it.
A switch mirror or SPAN port may be enough to copy traffic; a network TAP is another possible means, not an automatic requirement. Claroty describes the SPAN/mirror/monitor-port approach for passive collection in its passive monitoring overview. Nozomi Networks describes passive sensors and both on-premises and cloud management options for Guardian; confirm which options and dependencies apply to the exact proposal in its Guardian product information.
Compare the inventory’s operating workflow, not just its first scan
An inventory needs an owner and a maintenance process. Ask how the system reconciles discoveries with engineering records, handles duplicate or changing identities, assigns site and process context, tracks changes, and exports data to existing asset-management or security systems.
Best Value
- GOLD SECURITY PACK INCLUDED (1 YEAR): Anti-malware, sandboxing, IPS 1,000 Mbps, web filtering, DNS/IP/URL reputation, app patrol, AI SecuPilot, full UTM active from day one for small offices
- OFFLINE-CAPABLE SETUP AND UPDATES: Configure via Nebula portal wizard; update firmware offline via FTP on the local network, while the web interface remains fully accessible without internet after each update
- COMPACT FANLESS DESIGN: with SPI 2,000 Mbps firewall throughput, 1,000 Mbps IPS, 500 Mbps VPN, the firewall supports up to 25 users, 100,000 concurrent sessions, 20 IPSec tunnels, 15 SSL VPN users, and 8 VLANs
- FLEXIBLE SOFTWARE-DEFINED PORTS: 5 x 1G RJ-45 ports assignable as WAN or LAN, WAN load balancing, active-backup failover, 8 VLAN interfaces, and Link Aggregation for resilient connectivity
- NEBULA MANAGEMENT AND VPN: Centralized security policy control, real-time monitoring, and SD-VPN orchestration; supporting IKEv2/IPSec, SSL, Tailscale VPN, 20 IPSec tunnels, 15 SSL VPN users, and up to 12 managed APs
NIST’s 2026 project scope includes automated and manual discovery, inventory management, configuration management and change management. CISA also describes inventory as a foundation for lifecycle and vulnerability-management activities in its 2022 federal directive. These are reasons to assess ongoing inventory workflows, not proof that any one product implements them in a particular way.
Use a consistent scorecard for every candidate
Give each vendor the same evaluation script and ask for answers tied to your sites and representative assets. Record the evidence and gaps rather than treating a populated dashboard as proof of complete coverage.
| Evaluation area | Questions to answer |
|---|---|
| Discovery approach | Does the proposal use passive monitoring, queries, logs, APIs, configuration imports or a combination? What is sent to legacy devices? |
| Protocol and asset coverage | Does it identify installed models and protocol variants? Which attributes are observed, inferred or unknown? |
| Safety and operational fit | Can collection be piloted and approved under site procedures? What are the query failure modes? |
| Architecture | Where are sensors placed? What SPAN or TAP, bandwidth, segmentation, local-operation or cloud dependencies apply? |
| Inventory quality | How are duplicate identities, ownership, criticality, confidence, reconciliation, change history, exports and integrations handled? |
| Security functions | Which vulnerability details rely on observed data, queries, credentials, endpoint agents or external integrations? |
| Operations and cost | What staffing, updates, support, retention, licensing basis and implementation services are required, and what is the full lifecycle cost? |
Also record asset coverage, misidentifications and unknowns, deployment time, alert quality, staff effort and the update process. The sources available for this selection question do not establish independent comparative results, measured deployment effort or current prices. Obtain those details directly from vendors and document how they were determined.
Make the decision from evidence and documented gaps
Prefer the candidate that demonstrates useful identification on your representative equipment, fits site safety and network constraints, and supports the inventory workflow your teams can maintain. Keep unresolved coverage gaps visible in the procurement record. A platform’s own claims, including protocol counts, are vendor claims—not independent proof that it will identify your installed base.
Quick Recap
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