The invention relates to mobility management of an Internet-type protocol traffic in a mobile communications system. At least one mobile exchange (DXT1, DXT2) in the mobile communications system is arranged to operate as a gateway which interfaces (router 1) the mobile communications system with external data networks. All the mobile exchanges (DXT1, DXT2) are arranged to use a user identity and a data equipment identity for identifying each mobile host and to use an identity of the mobile exchange currently serving the mobile host for defining the location of the mobile host. Each mobile host is dynamically or permanently allocated an IP address which is bound to the user identity, the data equipment identity and the location information of the respective mobile host. The use of the user identity and the data terminal identity provide a unique identification for the mobile host without any relation to the IP network. Also the location information is independent of the IP network. As a consequence, the mobile exchanges are able to route IP datagrams having the allocated IP address from a gateway exchange (DXT1) to the serving exchange (DXT2) according to the location information and further to the respective mobile host according to the user identity and the data equipment identity bound to the IP address by using a mobile network specific routing method instead of mobile IP tunnelling.