What Max Masters Is
Max Masters is a BACnet MS/TP configuration parameter that defines the highest MAC address the token-passing algorithm will poll when looking for the next master device. It controls how far around the token ring the algorithm searches.
How It Affects the Network
| Max Masters Setting | Effect |
|---|---|
| Too low (e.g., 10) | Devices with MAC > 10 are excluded from token rotation — they never get to communicate |
| Too high (e.g., 127) | Algorithm polls empty addresses, wasting bus time — increases latency |
| Correctly matched | Token circulates efficiently among all active masters |
[!WARNING] Setting Max Masters lower than any device’s MAC address on the trunk silently excludes that device. It will appear “offline” even though it’s physically wired correctly.
Best Practice
Set Max Masters to the highest MAC address in use on the trunk, not higher. For example, if your devices use MACs 1, 5, and 12, set Max Masters to 12 on all masters.
[!NOTE] All master devices on the same trunk should use the same Max Masters value. Mismatched values cause inconsistent token behavior.