Lantronix
SM24TBT2DPA and SM24TBT2DPB Web User Guide
(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 Multi
802.1X variant.
Multi 802.1X is really not an IEEE standard, but features many of the same characteristics as does
port-based 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", that is, a dash (-) is used
as separator between the lower-cased hexadecimal digits. The switch only supports the MD5-
Challenge authentication 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 port-based 802.1X is that several clients can be
connected to the same port (e.g. through a 3rd party switch or a hub) and still require individual
authentication, and that the clients don't need special supplicant software to authenticate. 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, i.e.
Port-based 802.1X
and
Single 802.1X.
RADIUS attributes used in identifying a QoS Class: Refer to the written documentation for a description of
the RADIUS attributes needed in order to successfully identify a QoS Class.
The User-Priority-Table attribute defined in RFC4675 forms the basis for identifying the QoS Class
in an Access-Accept packet.
Only the first occurrence of the attribute in the packet will be considered, and to be valid, it must follow this
rule: