Method for diagnosing the availability of network subscribers (101, 102) in an IP-based network, in which each of the network subscribers (101, 102) can be allocated, in one or more address ranges (GUA, ULA, LLA), at least one respective address at which the relevant network subscriber (101, 102) is available to another network subscriber (101, 102, 103), wherein the network comprises: - a first network subscriber that has at least one respective first address allocated in at least one of the address ranges (GUA, ULA, LLA), wherein a first guideline that is stored in the first network subscriber stipulates which of the allocated first addresses needs to be used for communication with the other network subscribers (101, 102, 103); - a second network subscriber that has at least one respective second address allocated in at least one of the address ranges (GUA, ULA, LLA), wherein a second guideline that is stored in the second network subscriber stipulates which of the allocated second addresses needs to be used for communication with the other network subscribers (101, 102, 103); in which checking the availability of the second network subscriber to the first network subscriber involves the following steps being performed: a) the first network subscriber resolves a name of the second network subscriber, wherein the result obtained for the name resolution is the addresses of the address range(s) (GUA, ULA, LLA) that are allocated to the second network subscriber; b) an address list is produced using weighted address sorting from the addresses obtained in step a), so that the obtained addresses are sorted in ascending or descending order in accordance with their availability; c) for each of the addresses that the address list contains, separate examination of the communication capability between the first network subscriber and the second network subscriber is performed, wherein - the communication capability between the first network subscriber and the second network subscriber is examined by a diagnosis tool that sends a ping to each obtained address of the second network subscriber sequentially, - the pings are sequentially sent to the obtained addresses in the order of their weighted sorting, - the weighted address sorting is used to identify unavailable addresses of the second network subscriber and a ping examination is dispensed with for these unavailable addresses, and - the communication capability between the first network subscriber and the second network subscriber is examined under the control of a computation unit that controls the diagnosis tool; d) the result of the examination is evaluated and provided. - a first network subscriber that has at least one respective first address allocated in at least one of the address ranges (GUA, ULA, LLA), wherein a first guideline that is stored in the first network subscriber stipulates which of the allocated first addresses needs to be used for communication with the other network subscribers (101, 102, 103); - a second network subscriber that has at least one respective second address allocated in at least one of the address ranges (GUA, ULA, LLA), wherein a second guideline that is stored in the second network subscriber stipulates which of the allocated second addresses needs to be used for communication with the other network subscribers (101, 102, 103); a) the first network subscriber resolves a name of the second network subscriber, wherein the result obtained for the name resolution is the addresses of the address range(s) (GUA, ULA, LLA) that are allocated to the second network subscriber; b) an address list is produced using weighted address sorting from the addresses obtained in step a), so that the obtained addresses are sorted in ascending or descending order in accordance with their availability; c) for each of the addresses that the address list contains, separate examination of the communication capability between the first network subscriber and the second network subscriber is performed, wherein - the communication capability between the first network subscriber and the second network subscriber is examined by a diagnosis tool that sends a ping to each obtained address of the second network subscriber sequentially, - the pings are sequentially sent to the obtained addresses in the order of their weighted sorting, - the weighted address sorting is used to identify unavailable addresses of the second network subscriber and a ping examination is dispensed with for these unavailable addresses, and - the communication capability between the first network subscriber and the second network subscriber is examined under the control of a computation unit that controls the diagnosis tool; - the communication capability between the first network subscriber and the second network subscriber is examined by a diagnosis tool that sends a ping to each obtained address of the second network subscriber sequentially, - the pings are sequentially sent to the obtained addresses in the order of their weighted sorting, - the weighted address sorting is used to identify unavailable addresses of the second network subscriber and a ping examination is dispensed with for these unavailable addresses, and - the communication capability between the first network subscriber and the second network subscriber is examined under the control of a computation unit that controls the diagnosis tool; d) the result of the examination is evaluated and provided.