BACnet Invalid MAC Address
The BACnet stack rejects a MAC address that is out of range, malformed, or duplicates another node. MS/TP MAC addresses must be 0–127 and unique on the trunk.
Common Causes
- MAC address set to 255 (broadcast) or other reserved value
- Duplicate MAC address on the same MS/TP trunk
- Typo in router/gateway configuration (wrong network/MAC)
- Device firmware default (e.g., 0) conflicting with another node
Fix Steps
- Verify all MS/TP MAC addresses are 0–127 and unique; run MAC scan if available.
- Change conflicting MACs; document assignments to avoid future duplicates.
- Check router configuration: correct MS/TP network number and MAC for each port.
- Avoid using 0 or 255 unless required; prefer mid-range addresses for new devices.
- Update device configuration and restart; confirm in I-Am or network scan.