Cisco 7609-S Software Configuration Guide - Page 809

Chapter 46 Configuring IEEE 802.1X Port-Based Authentication Understanding 802.1X Port-Based Authentication When the router receives EAPOL frames and relays them to the authentication server, the Ethernet header is stripped and the remaining EAP frame is reencapsulated in the RADIUS format. The EAP frames are not modified or examined during encapsulation, and the authentication server must support EAP within the native frame format. When the router receives frames from the authentication server, the server's frame header is removed, leaving the EAP frame, which is then encapsulated for Ethernet and sent to the client. Authentication Initiation and Message Exchange The router or the client can initiate authentication. If you enable authentication on a port by using the dot1x port-control auto interface configuration command, the router must initiate authentication when it determines that the port link state transitions from down to up. The router then sends an EAP-request/identity frame to the client to request its identity (typically, the router sends an initial identity/request frame followed by one or more requests for authentication information). When the client receives the frame, it responds with an EAP-response/identity frame. If the client does not receive an EAP-request/identity frame from the router during bootup, the client can initiate authentication by sending an EAPOL-start frame, which prompts the router to request the client's identity. Note If 802.1X is not enabled or supported on the network access device, any EAPOL frames from the client are dropped. If the client does not receive an EAP-request/identity frame after three attempts to start authentication, the client transmits frames as if the port is in the authorized state. A port in the authorized state effectively means that the client has been successfully authenticated. For more information, see the "Ports in Authorized and Unauthorized States" section on page 46-4. When the client supplies its identity, the router begins its role as the intermediary, passing EAP frames between the client and the authentication server until authentication succeeds or fails. If the authentication succeeds, the router port becomes authorized. For more information, see the "Ports in Authorized and Unauthorized States" section on page 46-4. The specific exchange of EAP frames depends on the authentication method being used. Figure 46-2 shows a message exchange initiated by the client using the One-Time-Password (OTP) authentication method with a RADIUS server. OL-4266-08 Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX 46-3