A communication system is disclosed in which a control node generates configuration data for each of a plurality of MMEs operating in overlay networks. The configuration data defines a type of user equipment (UE) or a type of UE traffic to be serviced by each MME. The MME configuration data is provided to a base station and used to control selection of an MME to service a request from a UE. The control node monitors network traffic within and across the overlay networks and can reconfigure one or more MMEs to service different UE traffic types. This allows for improved flexibility in load balancing with overlay networks.