Wireless Local Area Network (WLAN) in IEEE802.11 standard is facing more complicated problem related security thread, which expose legitimated users to increased risk. Therefore, the security in WLAN network is very challenge in authentication. Extensible Authentication Protocol (EAP) is an authentication framework that is frequently used in wireless networks and Point to Point connections. For authentication purpose EAP used different methods to performed authentication. In this paper, the authors will explain each existing EAP authentication method, show the flow of every one and restriction.