Increasing the number of tunnelling connections on a KNX IP interface raises the count of additional individual addresses required.

Each simultaneous KNXnet/IP tunnelling connection needs its own dedicated individual address so that ETS or a visualisation client can be uniquely identified on the bus side. The device itself keeps its own individual address, and each extra tunnel slot consumes one further address in the line. Activating more parallel tunnels therefore directly increases the address budget you must reserve in the line.

Plan a small range of free individual addresses near the IP interface so future extra tunnelling clients can be assigned without renumbering.