iES28TG/iES28GF User Manual
154
iS5 Communications Inc.
Multi 802.1X
In port-based 802.1X authentication, once a supplicant is successfully
authenticated on a port, the whole port is opened for network traffic.
This allows other clients connected to the port (for instance through a
hub) to piggy-back on the successfully authenticated client and get
network access even though they are not authenticated individually. To
overcome this security breach, use the Multi 802.1X variant.
Multi 802.1X is not yet an IEEE standard, but features many of the same
characteristics as port-based 802.1X. In Multi 802.1X, one or more
supplicants can be authenticated on the same port at the same time. Each
supplicant is authenticated individually and secured in the MAC table using
the Port Security module.
In Multi 802.1X it is not possible to use the multicast BPDU MAC address as
the destination MAC address for EAPOL frames sent from the switch to the
supplicant, since that would cause all supplicants attached to the port to reply
to requests sent from the switch. Instead, the switch uses the supplicant's
MAC address, which is obtained from the first EAPOL Start or EAPOL
Response Identity frame sent by the supplicant. An exception to this is when
no supplicants are attached. In this case, the switch sends EAPOL Request
Identity frames using the BPDU multicast MAC address as destination - to
wake up any supplicants that might be on the port.
The maximum number of supplicants that can be attached to a port can be
limited using the Port Security Limit Control functionality.
