IP router as coupler to IP network - Basic Documentation - RMK770-1

Communication via the KNX bus

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10BaseT interface

The router can be connected to the IP network via Ethernet cable and the RJ45 socket of the IP router.

The IP router has a 10BaseT interface (Ethernet at 10 Mbps via Cat5 cable).


Observe the following rules when using IP routers:

  • With an IP router used as an area coupler (IP-Ac), no other IP routers may be installed below the IP-Ac in the topology.

  • With an IP router used as a line coupler (IP-Lc), no other IP routers may be installed above the IP-Lc in the topology.

Assign IP addresses

When IP routers are used for coupling to an IP network, the following issues must be discussed with the IP network administrator:

  • Automatic address assignment via DHCP (see Section 8.3),

  • Manual IP address assignment (see Section 8.3)
    and also:
    IP routing multicast. addr.
    IP subnet mask
    IP standard gateway


This document does not deal with the technical aspects of Ethernet communications.

Point-to-point connection

With a "point-to-point connection", the Ethernet cable forms area line 0, regardless of whether the coupling applies to two areas or lines (see figure) or one area with one line.

A crossed Ethernet cable is required to couple two IP routers.

Multiple connections

A switch box is required for multiple IP router connections. As part of the IP network, the switch box represents area line 0.

Use straight Ethernet cables to connect IP routers to the switch box.

IP router as area coupler

When the selected method of coupling is "IP router as area coupler", two or more KNX areas are linked via an IP network. The IP routers are used to link main lines, i.e. they must be addressed on the KNX side as area couplers.

KNX area 1 (main line 1) – IP network – KNX area 2 (main line 2)

IP routers as couplers between "worlds"

IP routers are also used to link "worlds". This method helps couple two or more KNX networks via an IP network

In this case, the IP routers connect the IP network to the KNX area line 0 of each involved KNX network. The IP routers in all KNX networks must be set to KNX address 0.0.0.

KNX network 1 (area line 0) – IP network – KNX network 2 (area line 0)