The present invention relates to a method and a ID-programming tool (30) for assigning a unique network entity identity number to a network entity (10). The network entity (10) is adapted to perform said method. The network entity (10) comprises a number of subscriber lines (12) and the network entity is adapted to perform at least one line condition test on said subscriber lines at a predefined occasion. Said subscriber lines are encoded to comprise a unique network entity identity number information by means of the ID-programming tool (30). Further, decoding means (42) is adapted to decode the network entity identity number information resulting from said test to gain said network entity identity number. Said network entity identity number is stored in a storage device (20) on the network entity (10).