802.1X authentication initiation
Both the 802.1X client and the access device can initiate 802.1X authentication.
802.1X client as the initiator
The client sends an EAPOL-Start packet to the access device to initiate 802.1X authentication. The destination MAC address of the packet is the IEEE 802.1X specified multicast address 01-80-C2-00-00-03 or the broadcast MAC address. If any intermediate device between the client and the authentication server does not support the multicast address, you must use an 802.1X client that can send broadcast EAPOL-Start packets. For example, you can use the iNode 802.1X client.
Access device as the initiator
If the client cannot send EAPOL-Start packets, configure the access device to initiate authentication. One example is the 802.1X client available with Windows XP.
The access device supports the following modes:
Multicast trigger mode—The access device multicasts EAP-Request/Identity packets to initiate 802.1X authentication at the identity request interval.
Unicast trigger mode—Upon receiving a frame from an unknown MAC address, the access device sends an EAP-Request/Identity packet out of the receiving port to the MAC address. The device retransmits the packet if no response has been received within the identity request timeout interval. This process continues until the maximum number of request attempts set by using the dot1x retry command is reached.
The username request timeout timer sets both the identity request interval for the multicast trigger and the identity request timeout interval for the unicast trigger.