Why should the BROADCAST gateway be avoided in KNX?

Owned by Wolfgang Granzer
Last updated: May 22, 2019

Communication with KNX devices and their data points is done via KNX group addresses. Since our server products are using IP as standard interface to the field/automation network, each KNX group address has to be assigned to a KNXnet/IP router or interface.

Within the server, the so called BROADCAST gateway is available. Please keep in mind that BROADCAST is NOT the same as KNXnet/IP routing. BROADCAST means “all KNXnet/IP routers and interfaces together”. Therefore, the BROADCAST shall only be used in rare, special cases. The reason is that, if you are sending a telegram to a KNX group address that is assigned to BROADCAST, the server is sending a group telegram to EACH gateway. If you have 50 gateways it will send 50 telegrams – one to each router. Since KNXnet/IP routers are also forwarding telegrams between their lines (based on filtering), you will have a lot of traffic there.

Therefore, BROADCAST should only be used in rare, special cases. For example:

  • if you have only one (1) KNXnet/IP router or interface
  • if only KNXnet/IP interfaces and no KNXnet/IP routers, line or backbone couplers are used
  • if you are using KNXnet/IP routers but all routers have KNXnet/IP routing deactivated (no routing between KNX lines).
  • for central commands that configured within the ETS

Article applies to the following products:

  • NETx BMS Platform
  • NETx Multi Protocol Server
  • NETx BMS Server 2.0