A method implemented by a first control plane server that is associated with a first radio access network (RAN) in which a user equipment is registered, the method comprising informing a network node about the location of the user equipment by the first control plane server, in accordance with a slave role assigned to the first control plane server, sending a signaling message to a second control plane server that is associated with a second RAN in which the user equipment is simultaneously registered, that is assigned a master role, and that is configured to perform control plane signaling on behalf of the first control plane server for informing the network node about said location.