Planet GS-5220 Series User Manual page 376

User's Manual of GS-5220 LCD Series
Single 802.1X
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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 really aren't authenticated. To
overcome this security breach, use the Single 802.1X variant.
Single 802.1X is really not an IEEE standard, but features many of the
same characteristics as does port-based 802.1X. In Single 802.1X, at
most one supplicant can get authenticated on the port at a time.
Normal EAPOL frames are used in the communication between the
supplicant and the switch. If more than one supplicant is connected to
a port, the one that comes first when the port's link comes up will be
the first one considered. If that supplicant doesn't provide valid
credentials within a certain amount of time, another supplicant will get
a chance. Once a supplicant is successfully authenticated, only that
supplicant will be allowed access. This is the most secure of all the
supported modes. In this mode, the Port Security module is used to
secure a supplicant's MAC address once successfully authenticated.
Multi 802.1X
Multi 802.1X is - like Single 802.1X - not an IEEE standard, but a variant
that features many of the same characteristics. In Multi 802.1X, one or
more supplicants can get 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 destination MAC address for EAPOL frames sent from the
switch towards 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. 376