What Is a Network Analyzer and How Does It Work?
Introduction
In the interconnected world of IT, OT, and industrial systems, network reliability, security, and performance are paramount. Whether you’re diagnosing a communication bottleneck, tracing a cyberattack, or validating new configurations, the network analyzer becomes an indispensable tool in your technical arsenal.
But what exactly is a network analyzer? How does it work? And why is it crucial for both enterprise and industrial networks?
This blog post will provide a complete, easy-to-follow explanation of network analyzers—ideal for system administrators, network engineers, OT technicians, cybersecurity analysts, and even curious students.
What Is a Network Analyzer?
A network analyzer is a tool—software or hardware—that captures, monitors, decodes, and analyzes the traffic traveling across a computer or industrial network.
Also known as:
- Packet sniffer
- Protocol analyzer
- Network protocol analyzer
- Traffic analyzer
Network analyzers give you visibility into every data packet moving between devices, allowing you to:
- Diagnose network issues
- Monitor bandwidth usage
- Identify security threats
- Understand communication protocols (e.g., TCP/IP, Modbus, PROFINET)
Types of Network Analyzers
| Type | Description | Use Case |
|---|---|---|
| Software-based | Applications like Wireshark, Microsoft Network Monitor | General IT and OT diagnostics |
| Hardware-based | Dedicated appliance (Fluke Networks, Keysight, NetScout) | High-traffic, mission-critical networks |
| Inline/Span Mode | Connected via TAP or SPAN port to passively monitor traffic | Non-intrusive industrial monitoring |
| Industrial Protocol Analyzers | Decode OT protocols like Modbus, EtherNet/IP, DNP3 | ICS/SCADA and PLC networks |
How a Network Analyzer Works
At its core, a network analyzer works by capturing packets that travel over a network interface and decoding the contents for analysis.
Step-by-Step Breakdown:
1. Packet Capture
- The analyzer uses a network interface card (NIC) in promiscuous mode to collect all packets (not just those addressed to it).
- It can capture from wired Ethernet, Wi-Fi, or mirrored switch ports.
2. Protocol Decoding
- Each packet is broken down into its layers (based on the OSI Model).
- The analyzer identifies:
- Source and destination IPs
- MAC addresses
- Protocol used (e.g., HTTP, FTP, Modbus)
- Payload data
3. Filtering and Aggregation
- Filters help isolate specific traffic (e.g., only HTTP or only traffic from IP
192.168.1.100). - Data can be aggregated by protocol, endpoint, or port.
4. Display and Analysis
- GUI shows live or recorded packet flow.
- Flags anomalies like:
- High latency
- Retransmissions
- Protocol violations
- Unauthorized devices
Common Features of Network Analyzers
| Feature | Purpose |
|---|---|
| Live packet capture | View traffic in real time |
| Deep packet inspection | Analyze data inside protocol headers |
| Protocol decoding | Understand application-layer details |
| Color-coded filters | Quickly highlight traffic types |
| Statistics view | Summarize by bandwidth, conversation, protocol |
| Export logs | Save captured data (PCAP format) for auditing or forensics |
| Alerts | Trigger alarms for unusual behavior (in advanced analyzers) |
Why Network Analyzers Matter in IT and OT
🧰 IT Network Troubleshooting
- Find slow connections, dropped packets, or DNS failures
- Validate routing and switching configurations
- Trace VoIP call quality or streaming issues
🔐 Cybersecurity and Threat Detection
- Spot unauthorized devices, port scanning, or malware activity
- Investigate lateral movement during cyber incidents
- Check for plaintext passwords or unencrypted protocols
🏭 Industrial Network Diagnostics
- Decode Modbus, PROFINET, BACnet, and EtherNet/IP
- Validate controller-to-controller communication
- Check timing, jitter, and traffic congestion in OT segments
- Assist with digital transformation and I/O mapping
Example: Using Wireshark in an OT Environment
Imagine you’re supporting an automation system where an HMI is not updating from a PLC. You use Wireshark on a mirrored switch port and see this:
- The HMI sends a Modbus request to the PLC.
- The PLC never responds.
- Upon inspection, the switch port to the PLC is down, or the PLC IP was changed.
Without a network analyzer, you’d be guessing.
Best Practices When Using a Network Analyzer
| Practice | Benefit |
|---|---|
| Use SPAN or TAP | Avoid interfering with production networks |
| Apply filters early | Reduces noise and data overload |
| Know your protocols | Easier to interpret traffic meaningfully |
| Set proper capture limits | Avoid filling storage or impacting system performance |
| Keep captures secure | PCAP files may contain sensitive data |
Common Tools Used as Network Analyzers
| Tool | Description | Use |
|---|---|---|
| Wireshark | Most popular open-source packet sniffer | General IT/OT packet capture |
| tcpdump | CLI-based tool for Linux | Scripting, remote diagnostics |
| Tshark | CLI version of Wireshark | Automation, server-side capture |
| SolarWinds NPM | GUI-based, enterprise-grade | Proactive monitoring, trending |
| Fluke OneTouch | Hardware-based analyzer | Field service and validation |
| SCADAfence, Nozomi | Industrial security analyzers | OT anomaly detection |
Network Analyzer and the OSI Model
A network analyzer is a versatile tool because it helps dissect traffic at all seven layers of the OSI model:
| OSI Layer | What Analyzer Shows |
|---|---|
| Layer 1 – Physical | Link up/down, cable failures (limited in software analyzers) |
| Layer 2 – Data Link | MAC addresses, ARP requests |
| Layer 3 – Network | IP addressing, subnet routing |
| Layer 4 – Transport | TCP/UDP ports, retransmissions, latency |
| Layer 5 – Session | Session timeouts or resets |
| Layer 6 – Presentation | Encoding types, compression |
| Layer 7 – Application | HTTP, DNS, SMB, Modbus data |
When to Use a Network Analyzer
✅ During network slowdowns or outages
✅ To verify network security and segmentation
✅ Before and after configuration changes
✅ When onboarding new industrial devices
✅ For forensic analysis after a cyber incident
Limitations and Considerations
- Encrypted traffic like HTTPS can’t be fully analyzed without keys.
- Heavy traffic may overwhelm software analyzers.
- Legal and ethical concerns—always ensure you have permission to capture traffic, especially in regulated environments.
- In ICS/SCADA networks, non-intrusive capture is critical—never disrupt live control systems.
Summary Table
| Aspect | Network Analyzer Details |
|---|---|
| Definition | Tool to monitor and analyze network traffic |
| Types | Software, hardware, protocol-specific |
| Common Tools | Wireshark, tcpdump, Fluke, Nozomi |
| Uses | Troubleshooting, security, OT diagnostics |
| Capture Method | Promiscuous mode or port mirroring |
| File Format | PCAP, PCAPNG |
| Protocols Supported | TCP/IP, UDP, HTTP, DNS, Modbus, SNMP, etc. |
Conclusion
A network analyzer is one of the most powerful tools in a technician’s toolbox—whether in IT, OT, or hybrid environments. It gives you deep visibility into network behavior, enabling you to troubleshoot issues, detect threats, validate configurations, and even learn how protocols work under the hood.
If you want to move from guessing to knowing what’s happening on your network, a network analyzer is not optional—it’s essential.
Whether you’re using Wireshark in a home lab or deploying Nozomi on an OT floor, mastering network analysis will make you a more proactive, skilled, and security-aware professional.
FAQs
Q1: Is Wireshark safe to use in production?
Yes, if used in passive monitoring mode (e.g., via a SPAN port). Never run intrusive scans on ICS/SCADA networks.
Q2: Can I analyze encrypted traffic?
You can see encrypted packet headers, but not content unless you have access to the private keys or are using SSL inspection.
Q3: What’s the difference between a network analyzer and a firewall?
A network analyzer observes and reports on traffic. A firewall controls or blocks traffic based on rules.