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venfree/Wiki/KNXnet/IP – KNX over IP Networks

KNXnet/IP – KNX over IP Networks

KNXnet/IP is the standard for KNX communication over IP networks. It enables remote ETS programming (tunneling) and connects multiple TP lines via an IP backbone (routing).

Tunneling and Routing

Tunneling connects an ETS computer via UDP to a KNX IP interface or IP router. The device translates KNXnet/IP packets to TP telegrams and vice versa. A maximum of 4 simultaneous tunnel connections per device are supported.

Routing connects two lines via IP as a backbone. The IP router forwards telegrams via IP multicast (standard address 224.0.23.12, UDP port 3671). This allows the physical TP backbone coupler to be replaced by a LAN connection.

Security Note

KNXnet/IP without Secure transmits telegrams in plain text on the LAN. Port 3671 should never be opened directly to the internet, without KNX IP Secure, the entire bus can be controlled from outside. For remote access: use VPN or KNX IP Secure.

Key Facts

  • Protocol: UDP, port 3671
  • Multicast address for routing: 224.0.23.12
  • Max. 4 tunnel connections per device
  • IP router = line coupler over IP
  • IP interface = tunneling only, no routing
  • Never open port 3671 to the internet without VPN or KNX Secure

Related Articles

KNX Line Coupler and Area Coupler
A KNX line coupler (LC) connects two lines and filters telegrams, only telegrams with destination GAs in the filter table are forwarded. It reduces bus load and provides galvanic isolation.
KNX IP Interface
A KNX IP interface connects an ETS computer to the KNX bus over the LAN. Unlike an IP router, it does not forward telegrams between lines, it is exclusively a gateway for ETS and visualisation systems.
KNX Secure – Encryption for the Bus
KNX Secure is the security standard for KNX communication. It protects bus telegrams against eavesdropping and manipulation, both on IP networks (IP Secure) and on the TP cable (Data Security).
KNX Topology
KNX TP networks are hierarchically structured: devices form a line, lines are grouped into areas, areas are connected via the backbone. This structure supports up to 14,400 devices in a pure TP network.

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