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:
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 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
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LANCOM GS-2310P/GS-2326(P) User Manual
5 Security
