The current invention relates to a method for a network attachment procedure and a user equipment in a wireless mobile network, the wireless mobile network comprising a user equipment with a temporary identity and at least one mobility management entity. The method comprises the steps of providing an estimation whether the user equipment is unknown at the mobility management entity and sending the user equipment's temporary identity during the network attachment procedure. If the user equipment has been estimated to be unknown at the at least one mobility management entity, the user equipment's identity is sent during the network attachment procedure. These steps are carried out by the user equipment.