PROFINET Network Discovery With OTserver
Overview
PROFINET Discovery and Configuration Protocol (DCP) exposes identity and network attributes on the local Ethernet segment. OTserver uses DCP because it can find PROFINET devices by MAC address even before their IP configuration is known.
How OTserver discovers PROFINET devices
The scanner sends a DCP Identify All Ethernet frame to multicast MAC address 01:0E:CF:00:00:00 with EtherType 0x8892. It matches replies to the request transaction ID and rejects malformed, truncated, or unrelated frames.
On Linux, OTserver binds a native AF_PACKET raw socket to the selected interface. Active discovery sends one Identify-All request with response-delay factor 0x0080, spreading device replies across the capture window instead of creating a response burst. On Windows, active discovery uses a separately installed Npcap driver on the selected physical adapter and verifies that the source MAC belongs to that adapter. If that driver is unavailable, Microsoft pktmon provides passive PROFINET observation with Administrator rights but cannot transmit Identify requests.
Evidence extracted
| OTserver evidence | DCP source |
|---|---|
| MAC address | Ethernet source and DCP MAC block |
| IP address, network mask, gateway | IP parameter block |
| DNS servers | Full IP parameter block |
| Device name | Name of Station |
| Model | Device Vendor Value |
| Vendor ID and device ID | Device ID block |
| Device role | IO device, controller, multidevice, or supervisor flags |
| Additional evidence | Alias, instance, OEM IDs, options, and configuration-domain data |
OTserver warns when the advertised MAC differs from the Ethernet source or when DCP reports an IP-address conflict. Unknown DCP blocks remain available as raw evidence.
Security and read-only safety
OTserver sends DCP Identify only. It does not send DCP Set or change a station name, IP address, or other device configuration. Layer 2 discovery still reaches every responding PROFINET device on the local segment, so use it only on networks you own or are authorized to assess.
Frequently asked questions
Does PROFINET discovery require an IP address?
No. DCP Identify operates directly at Ethernet Layer 2. The selected scanner interface must share the device’s broadcast domain; routers do not normally forward these frames.
Does OTserver need a special Windows network bridge?
No. Active Windows discovery binds Npcap to the selected physical adapter. The scanner does not create a TAP adapter or Windows Network Bridge.
Compare all supported discovery protocols or configure the scanner.