Apparatuses, methods, and systems are disclosed for authenticating with a mobile communication network. One apparatus includes a processor, a first transceiver that communicates with a mobile communication network via a first access network, and a second transceiver that communicates with the mobile communication network via a second access network. The processor sends a request to start authentication via the second access network and receives an extensible authentication protocol (“EAP”) request with a first expanded type via the second access network. The processor sends an EAP response via the second access network, the EAP response comprising the first expanded type, a first set of parameters, and a first message. Here, the first message is a same type of message usable to establish a connection with the mobile communication network over the first access network.