What NM-RC-B Is
NM-RC-B (Network Management-Router Configuration-B) is the BACnet Interoperability Building Block (BIBB) for a device acting as a router: it covers the network-layer peer messages a B-router answers to discover routes, bootstrap and maintain a routing table, signal congestion, and report unroutable traffic. The full message-by-message reference covers each one in detail.
What It Requires
| Message group | What it covers |
|---|---|
| Discovery | Who-Is-Router-To-Network and I-Am-Router-To-Network |
| Bootstrap | Initialize-Routing-Table and its acknowledgment |
| Error | Reject-Message-To-Network |
| Flow control | Router-Busy-To-Network and Router-Available-To-Network |
| Network identity | Network-Number-Is and its query |
Half-router connection establishment (Establish-Connection-To-Network and Disconnect-Connection-To-Network) is a narrower, separately-verified case; the network-layer messages exist, but the command path is not independently confirmed on every claiming device.
Where You Meet It in the Field
Any device sitting at the boundary between two BACnet networks, whether that boundary is two MS/TP trunks, a BACnet/IP segment and an MS/TP trunk, or two IP network numbers, is claiming NM-RC-B. It matters most the moment a real network condition exercises a message the router was never tested against: a congested downstream network, an unroutable message, a routing-table bootstrap after a topology change.
[!NOTE] A router that handles the discovery pair correctly can still be silent on flow control or error reporting. Confirm which specific peer messages a device answers rather than assuming NM-RC-B support means every message in the set is exercised equally.
What Chipkin Provides
The CAS BACnet Stack supports NM-RC-B today: each peer message above has a dedicated test, plus a broader router and network-layer test panel exercising the routing-table state machine end to end. This is test-suite evidence, not a BTL profile run. Talk to us about your specific routing boundary.