IP address planning for automation projects
A practical scheme for plant IP addressing: private ranges, one subnet per cell/VLAN, address blocks per device class, gateways, documentation and pitfalls with machine builders.
An IP address plan is part of the design documentation, like the I/O list. A good plan makes commissioning, replacement and troubleshooting predictable and supports network segmentation.
Principles
- Use private ranges (RFC 1918): 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16. Coordinate with IT so plant ranges never overlap office or VPN ranges.
- One subnet per VLAN/zone: e.g. a /24 per production cell, separate subnets for SCADA servers, engineering, remote I/O islands, cameras.
- Fixed address blocks per device class inside each subnet, the same in every cell.
- Gateway on a fixed address (commonly .1 or .254) — decide once for the whole site.
- Static addresses for controllers and field devices; DHCP only for laptops/clients in dedicated ranges.
Example layout for a /24 cell (10.20.| .0/24) |
| Range | Devices |
|---|---|
| .1 | Gateway / firewall |
| .2–.9 | Switches (management) |
| .10–.19 | PLCs / controllers |
| .20–.39 | HMIs, panel PCs |
| .40–.99 | Drives |
| .100–.179 | Remote I/O, valve islands, IO-Link masters |
| .180–.199 | Robots, vision, special devices |
| .200–.239 | Reserved |
| .240–.250 | Service laptops (temporary) |
Machine builders and NAT
OEM machines often arrive with identical internal addresses (192.168.0.x). Instead of re-addressing every machine, use 1:1 NAT routers/firewalls at the machine boundary and document both the internal and plant addresses.
Documentation
Keep one maintained list: device tag, IP, mask, gateway, VLAN, switch and port, MAC, PROFINET device name, firmware. Export it to the project archive at every handover.
Connections
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Sources
Updated 2026-10-04