The KNX standard for home and building automation has been recently updated by the definition of KNXnet/IP system. It allows integration of different KNX networks through IP using the KNXnet/IP Router. Due to the limited transmission speeds of the KNX, the KNXnet/IP Router may represent a bottleneck. The aim of the paper is to analyse the effect of congestion of KNXnet/IP Router on the information flow exchanged between different KNX networks; furthermore, the analysis will focus on the impact of the two policies available inside the KNXnet/IP Router to forward telegrams coming from IP towards the relevant KNX network.