A method of allocating users to core network nodes of a cellular telecommunications System, where users access the core network via a radio access network and where the nodes of the core network are grouped into a plurality of local pool areas and the local pool areas are further grouped into one or more pool areas, and each local pool area corresponds to a geographic area covered by the access network. The method comprises allocating a user to a core network node of a local pool area corresponding to the geographic area within which the user is located, maintaining the core network node while the user moves within the local pool area, and, in the event that the user moves out of the local pool area but remains in the same pool area, maintaining said allocation at least temporarily.