A wireless telecommunication system may utilize multiple network slices, each of which may implement a different core network. In order to route initial attach requests to appropriate network slices and corresponding core networks, a mobility management component sends a received initial attach request to a network slice selector. The network slice selector queries a selection policy function to obtain a designation of a particular network slice to which the attach request should be directed. The network slice selector then sends a redirect request to the mobility management component, instructing the mobility management component to resend the attach request to the designated network slice.