BACnet Network Port Object

The BACnet Network Port object (Clause 12.56) models a device's network interface: its IP, IPv6, BBMD, and MS/TP settings

Categories:

BACnet

Tags:

Bacnet Object Type Network Port

Updated

Jul 16, 2026

What the Network Port Object Is

The Network Port object, defined in Clause 12.56 of ANSI/ASHRAE 135-2024, models one network interface of a BACnet device: an Ethernet BACnet/IP port, an MS/TP (Master-Slave/Token-Passing) trunk, a BACnet SC connection, and so on. A device has one Network Port object per interface, and the object exposes that interface’s addressing and datalink settings as readable and writable BACnet properties.

Its purpose is runtime configuration. Before the Network Port object, changing a device’s IP address or BACnet BBMD table meant a vendor tool; the Network Port object standardizes those settings so any BACnet client can read and change them. Writes are staged, not applied immediately: Changes_Pending flags that edits are waiting, and a ReinitializeDevice request with ACTIVATE_CHANGES commits them. Writing Command with discard-changes throws the staged edits away instead; the other Command values act on the port directly and are not the commit path.

Where You’ll See It

IP and network commissioning. Reading and setting a device’s IP address, subnet mask, gateway, and BACnet/IP UDP port over BACnet instead of a serial tool.
BBMD configuration. Editing the Broadcast Distribution Table and viewing the Foreign Device Table (populated by registration, not by write) on a device acting as a BACnet BBMD.
MS/TP tuning. Reading Max_Master and Max_Info_Frames on an MS/TP port. Reading Network Port 4194303 (the wildcard) with ReadProperty returns the port that received the request.

Required Properties

Clause 12.56 requires every Network Port object to provide these properties. Datatypes are the spec’s names: Unsigned is an integer, REAL a floating-point number, BOOLEAN a true/false flag, and the BACnet-prefixed types are structured values defined by the standard.

Property	Datatype	What it holds
`Object_Identifier`	BACnetObjectIdentifier	The object’s type and instance number, unique within the device
`Object_Name`	CharacterString	The human-readable interface name
`Object_Type`	BACnetObjectType	Always `network-port` for this object
`Status_Flags`	BACnetStatusFlags	Four health flags: in-alarm, fault, overridden, out-of-service
`Reliability`	BACnetReliability	Why the port is unreliable, if it is
`Out_Of_Service`	BOOLEAN	When true, the port is decoupled for testing
`Network_Type`	BACnetNetworkType	The datalink type (`ipv4`, `ipv6`, `mstp`, `ethernet`, `secure-connect`)
`Protocol_Level`	BACnetProtocolLevel	The protocol level the port operates at
`Network_Number`	Unsigned	The BACnet network number this port connects to
`Network_Number_Quality`	BACnetNetworkNumberQuality	How the network number was learned (configured, learned, unknown)
`Changes_Pending`	BOOLEAN	True when edited properties are staged but not yet applied
`APDU_Length`	Unsigned	The maximum APDU (Application Protocol Data Unit) length for this port
`Link_Speed`	REAL	The datalink speed, in bits per second
`Property_List`	BACnetARRAY[N] of BACnetPropertyIdentifier	The list of properties this instance implements

Optional Properties

Most of the Network Port object is optional because the relevant set depends on the interface type: an IPv4 port implements the IP_* group, an MS/TP port the Max_Master and slave-proxy group, a BACnet BBMD the BBMD_* group. The properties integrators touch most are IP_Address, IP_Subnet_Mask, IP_Default_Gateway, and the BBMD_Broadcast_Distribution_Table.

Property	Datatype	Group
`Description`	CharacterString	General
`Reference_Port`	Unsigned	General
`Command`	BACnetNetworkPortCommand	General
`MAC_Address`	OctetString	General
`Link_Speeds`	BACnetARRAY[N] of REAL	General
`Link_Speed_Autonegotiate`	BOOLEAN	General
`Network_Interface_Name`	CharacterString	General
`BACnet_IP_Mode`	BACnetIPMode	BACnet/IP
`IP_Address`	OctetString	BACnet/IP
`BACnet_IP_UDP_Port`	Unsigned	BACnet/IP
`IP_Subnet_Mask`	OctetString	BACnet/IP
`IP_Default_Gateway`	OctetString	BACnet/IP
`BACnet_IP_Multicast_Address`	OctetString	BACnet/IP
`IP_DNS_Server`	BACnetARRAY[N] of OctetString	BACnet/IP
`IP_DHCP_Enable`	BOOLEAN	BACnet/IP
`IP_DHCP_Lease_Time`	Unsigned	BACnet/IP
`IP_DHCP_Lease_Time_Remaining`	Unsigned	BACnet/IP
`IP_DHCP_Server`	OctetString	BACnet/IP
`BACnet_IP_NAT_Traversal`	BOOLEAN	BACnet/IP
`BACnet_IP_Global_Address`	BACnetHostNPort	BACnet/IP
`BBMD_Broadcast_Distribution_Table`	BACnetLIST of BACnetBDTEntry	BACnet BBMD
`BBMD_Accept_FD_Registrations`	BOOLEAN	BACnet BBMD
`BBMD_Foreign_Device_Table`	BACnetLIST of BACnetFDTEntry	BACnet BBMD
`FD_BBMD_Address`	BACnetHostNPort	Foreign device
`FD_Subscription_Lifetime`	Unsigned16	Foreign device
`BACnet_IPv6_Mode`	BACnetIPMode	BACnet/IPv6
`IPv6_Address`	OctetString	BACnet/IPv6
`IPv6_Prefix_Length`	Unsigned	BACnet/IPv6
`BACnet_IPv6_UDP_Port`	Unsigned	BACnet/IPv6
`IPv6_Default_Gateway`	OctetString	BACnet/IPv6
`BACnet_IPv6_Multicast_Address`	OctetString	BACnet/IPv6
`IPv6_DNS_Server`	BACnetARRAY[N] of OctetString	BACnet/IPv6
`IPv6_Auto_Addressing_Enable`	BOOLEAN	BACnet/IPv6
`IPv6_DHCP_Lease_Time`	Unsigned	BACnet/IPv6
`IPv6_DHCP_Lease_Time_Remaining`	Unsigned	BACnet/IPv6
`IPv6_DHCP_Server`	OctetString	BACnet/IPv6
`IPv6_Zone_Index`	CharacterString	BACnet/IPv6
`Max_Master`	Unsigned	MS/TP
`Max_Info_Frames`	Unsigned	MS/TP
`Slave_Proxy_Enable`	BOOLEAN	MS/TP
`Manual_Slave_Address_Binding`	BACnetLIST of BACnetAddressBinding	MS/TP
`Auto_Slave_Discovery`	BOOLEAN	MS/TP
`Slave_Address_Binding`	BACnetLIST of BACnetAddressBinding	MS/TP
`Max_BVLC_Length_Accepted`	Unsigned16	BACnet SC
`Max_NPDU_Length_Accepted`	Unsigned16	BACnet SC
`SC_Primary_Hub_URI`	CharacterString	BACnet SC
`SC_Failover_Hub_URI`	CharacterString	BACnet SC
`SC_Minimum_Reconnect_Time`	Unsigned16	BACnet SC
`SC_Maximum_Reconnect_Time`	Unsigned16	BACnet SC
`SC_Connect_Wait_Timeout`	Unsigned16	BACnet SC
`SC_Disconnect_Wait_Timeout`	Unsigned16	BACnet SC
`SC_Heartbeat_Timeout`	Unsigned16	BACnet SC
`SC_Hub_Connector_State`	BACnetSCHubConnectorState	BACnet SC
`SC_Primary_Hub_Connection_Status`	BACnetSCHubConnection	BACnet SC
`SC_Failover_Hub_Connection_Status`	BACnetSCHubConnection	BACnet SC
`SC_Hub_Function_Enable`	BOOLEAN	BACnet SC
`SC_Failed_Connection_Requests`	BACnetLIST of BACnetSCFailedConnectionRequest	BACnet SC
`SC_Hub_Function_Accept_URIs`	BACnetARRAY[N] of CharacterString	BACnet SC
`SC_Hub_Function_Binding`	CharacterString	BACnet SC
`SC_Hub_Function_Connection_Status`	BACnetLIST of BACnetSCHubFunctionConnection	BACnet SC
`SC_Direct_Connect_Initiate_Enable`	BOOLEAN	BACnet SC
`SC_Direct_Connect_Accept_Enable`	BOOLEAN	BACnet SC
`SC_Direct_Connect_Accept_URIs`	BACnetARRAY[N] of CharacterString	BACnet SC
`SC_Direct_Connect_Binding`	CharacterString	BACnet SC
`SC_Direct_Connect_Connection_Status`	BACnetLIST of BACnetSCDirectConnection	BACnet SC
`Operational_Certificate_File`	BACnetObjectIdentifier	BACnet SC
`Issuer_Certificate_Files`	BACnetARRAY[N] of BACnetObjectIdentifier	BACnet SC
`Certificate_Signing_Request_File`	BACnetObjectIdentifier	BACnet SC
`Virtual_MAC_Address_Table`	BACnetLIST of BACnetVMACEntry	Routing
`Routing_Table`	BACnetLIST of BACnetRouterEntry	Routing
`Event_Detection_Enable`	BOOLEAN	Intrinsic reporting
`Notification_Class`	Unsigned	Intrinsic reporting
`Event_Enable`	BACnetEventTransitionBits	Intrinsic reporting
`Acked_Transitions`	BACnetEventTransitionBits	Intrinsic reporting
`Notify_Type`	BACnetNotifyType	Intrinsic reporting
`Event_Time_Stamps`	BACnetARRAY[3] of BACnetTimeStamp	Intrinsic reporting
`Event_Message_Texts`	BACnetARRAY[3] of CharacterString	Intrinsic reporting
`Event_Message_Texts_Config`	BACnetARRAY[3] of CharacterString	Intrinsic reporting
`Event_State`	BACnetEventState	Intrinsic reporting
`Reliability_Evaluation_Inhibit`	BOOLEAN	Intrinsic reporting
`Audit_Level`	BACnetAuditLevel	Auditing
`Auditable_Operations`	BACnetAuditOperationFlags	Auditing
`Tags`	BACnetARRAY[N] of BACnetNameValue	Tagging and profile
`Profile_Location`	CharacterString	Tagging and profile
`Profile_Name`	CharacterString	Tagging and profile

The BACnet SC Property Group

On a BACnet Secure Connect port, the Network Port object is the whole configuration and diagnostic surface for the datalink. Annex AB defines no separate management protocol, so the properties above are how a BACnet client reads and changes BACnet SC behavior.

Hub connection. SC_Primary_Hub_URI and SC_Failover_Hub_URI are the wss:// addresses the node connects outbound to. SC_Hub_Connector_State reports which one is active. Hub redundancy lives here, on the node, not on the hub: the node decides when to fall back.
Why a node was rejected. SC_Failed_Connection_Requests records the timestamp, peer address, VMAC, UUID, and error for each connection attempt this device refused, whether the hub function turned it away or direct-connect accept did. When a controller silently will not join, this is the first property to read on the device that rejected it. It is usually the difference between “certificate expired” and “clock skew”, without a packet capture you could not decrypt anyway.
The hub function. SC_Hub_Function_Enable is what turns a node into the hub. SC_Hub_Function_Connection_Status lists the nodes currently connected, which is the fastest answer to “is that controller actually online.”
Direct connect. The initiate and accept enables are separate properties, so a device can accept peer connections without ever opening one, or the reverse. See NM-SCDC-B.
Certificates. Operational_Certificate_File, Issuer_Certificate_Files, and Certificate_Signing_Request_File point at File objects, which is what lets certificate provisioning run over ordinary atomic file transfer. See NM-SCCM-A.
Reconnect behavior. SC_Minimum_Reconnect_Time and SC_Maximum_Reconnect_Time bound the backoff a node uses after losing the hub. They exist because a hub restart on a site with hundreds of nodes is a thundering herd, and the randomized window between the two values is what spreads the reconnect storm out.

Device: summarizes the device’s identity and capabilities; the Network Port objects carry the per-interface network detail.

The Network Port object is also where BACnet BBMD tables and device-address proxying are configured, the surface NM-BBMDC-B and NM-RC-B require a device to expose.

What Chipkin Provides

The Network Port object, including the BACnet/IP, IPv6, BBMD, MS/TP, and BACnet SC property groups and the staged-changes model, is implemented in the CAS BACnet Stack, exposed for read in 5.x. Two caveats: automatic fallback from the primary to the failover BACnet SC hub URI is a CAS BACnet Stack 6.x item, so do not design 5.x redundancy around it (see BACnet SC in the CAS BACnet Stack); and BDT writes landing end to end through standard WriteProperty are also a 6.x target rather than a 5.x capability (see How BACnet Networks Scale). Talk to us about modeling your device’s points.