Abstract IP geolocation technology based on network measurement can provide IP geographic location capability without user assistance. In the case that the IP target device or intermediate route device does not respond to the detection message, the existing geolocation methods have reduced the accuracy of city-level geolocation, not to mention that the target cannot be located within the city. To solve this problem, a geolocation method for unreachable IP (called GUI) is proposed. GUI first extracts the target city metropolitan area network (MAN) topology, obtains the path to the IP target and compares it with the MAN topology to achieve the city-level geolocation of the target, and then looks for landmarks in the database that belong to the same /24 subnet and the same city-level location with the target. If the above landmarks exist, GUI uses the coordinate set corresponding to the landmarks to solve the minimum covering circle, so as to judge the location of the target. If the above landmarks do not exist, GUI searches for the intersection nodes from the target detection path and MAN topology, enumerates the connected landmarks, calculates the minimum covering circle according to the coordinates and uses it for the target’s urban internal geolocation. The experimental results of 15 cities in China and the USA show that GUI can effectively geolocate IP targets. The city-level geolocation success rate of reachable IP can reach 99.41%, that of unreachable IP can reach 89.37% and the minimum median error of urban internal unreachable IP geolocation can reach 4.99km. All indicators are significantly better than the existing typical geolocation methods, such as PoP-Based Geolocation, Street-Level Geolocation, Ranking Nodes Based Geolocation, and the existing typical IP geographic location databases such as IPIP and MaxMind.