System, computer program and method for determining a transmission path of datagrams in an IP network from a source device to a destination device. The source device receives from a network manager station, a message for retrieving information related to the transmission path of datagrams to the destination device. The message comprises a destination address and a source address. The destination address is an IP address of the destination device, and the source address is an IP address of the network manager device. The source device sends a plurality of probe datagrams to a respective plurality of IP network devices along the transmission path to the destination device. Each probe datagram comprises as destination address, the IP address of the destination device and as source address, the IP address of the network manager station. Consequently, replies, if any, to the probe datagrams are sent back directly to the network manager station by the IP network device along the transmission path, bypassing said the device. The invention also resides in the network manager station and the computer program product executing at the network manager station which sends the message to the source device, and receives and analyzes the replies to the probe datagrams to locate the break in the transmission path.