What is an IP address?
An IP address (Internet Protocol address) is a unique identification number assigned to a device on a network so that it can send and receive data via IP-based protocols such as TCP, UDP or HTTP.
In OT networks, IP addresses are essential to enable communication between PLCs, HMIs, SCADA, Drives, Remote IO and other industrial components.
🧠 How does an IP address work?
- Each network device receives a unique IP address within a subnet.
- IP addresses are used at Layer 3 of the OSI model for routing between networks.
- An IP address can be statically assigned or automatically via DHCP or BOOTP.
- Communication takes place via IP packets, which use MAC addresses for local delivery (via ARP).
A typical IPv4 address looks like
192.168.1.10. IPv6 addresses are longer and more complex.
🏭 Application of IP addresses in industrial networks
- Assignment of fixed IPs to PLCs for reliable communication
- Used for access to HMIs, web servers or embedded configuration tools
- Network segmentation based on IP ranges in line with the Purdue Model
- Monitoring and logging via SNMP, Syslog, SCADA and SIEM
- Firewall rules and ACLs based on source/destination IP addresses
In OT environments, IP addresses are typically manually managed to ensure stability and predictability.
🔍 IPv4 vs. IPv6
| Aspect | IPv4 | IPv6 |
|---|---|---|
| Address length | 32 bits (e.g. 192.168.1.1) | 128 bits (e.g. 2001:0db8:85a3::8a2e:0370:7334) |
| Notation | Dotted decimal | Hexadecimal with colons |
| Total addresses | ~4.3 billion | More than 10^38 |
| Use in OT | Standard | Rare – limited support in industrial equipment |
| Configuration | Simple, recognisable | More complex, often automatic |
🔐 Security aspects
- IP spoofing can mislead systems – combine with MAC address checks
- Restrict access to sensitive IP ranges with Firewall, VLAN or ACL
- Use network segmentation to separate IP ranges per zone in line with the Purdue Model
- Implement IP traffic logging via SIEM, IDS or Syslog
- IP address management is crucial for preventing unwanted communication or network conflicts
In industrial networks, the use of predictable, documented IP schemes is a best practice.
📌 In summary
The IP address is the key to communication in modern networks, in both IT and OT. In industrial environments, structured IP usage supports reliability, security and manageability of networks.