Transition Networks
S4224 Web User Guide
33558 Rev. C
Page 98 of 669
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. 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.
MAC-based Auth.
:
Unlike port-based 802.1X, MAC-based authentication is not a standard, but
merely a best-practices method adopted by the industry. In MAC-based authentication, users are
called clients, and the switch acts as the supplicant on behalf of clients. The initial frame (any kind of
frame) sent by a client is snooped by the switch, which in turn uses the client's MAC address as both
username and password in the subsequent EAP exchange with the RADIUS server. The 6-byte MAC
address is converted to a string on the following form "
xx-xx-xx-xx-xx-xx
" or "
xx.xx.xx.xx.xx.xx
" or
"
xxxxxxxxxxxx
" (x is a hexadecimal digit). The switch only supports the
method, so the RADIUS server must be configured accordingly.
When authentication is complete, the RADIUS server sends a success or failure indication, which in
turn causes the switch to open up or block traffic for that particular client, using the Port Security
module. Only then will frames from the client be forwarded on the switch. There are no EAPOL
frames involved in this authentication, and therefore, MAC-based Authentication has nothing to do
with the 802.1X standard.
The advantage of MAC-based authentication over 802.1X-based authentication is that the clients
don't need special supplicant software to authenticate. The disadvantage is that MAC addresses can
be spoofed by malicious users (equipment whose MAC address is a valid RADIUS user can be used
by anyone). Also, only the MD5-Challenge method is supported. The maximum number of clients that
can be attached to a port can be limited using the Port Security Limit Control functionality.
RADIUS-Assigned QoS Enabled
When RADIUS-Assigned QoS is both globally enabled and enabled (checked) on a given port, the
switch reacts to QoS Class information carried in the RADIUS Access-Accept packet transmitted by
the RADIUS server when a supplicant is successfully authenticated. If present and valid, traffic
received on the supplicant's port will be classified to the given QoS Class. If (re-)authentication fails or
the RADIUS Access-Accept packet no longer carries a QoS Class or it's invalid, or the supplicant is
otherwise no longer present on the port, the port's QoS Class is immediately reverted to the original
QoS Class (which may be changed by the administrator in the meanwhile without affecting the
RADIUS-assigned).
This option is only available for single-client modes:
• Port-based 802.1X
• Single 802.1X
