iES26GF
User’s
Manual
UM-iES26GF-1.2.3-EN.docx
Pages 121 of 169
Since the server has not failed (because the X seconds have not expired), the same server will be
contacted when the next back-end authentication server requests from the switch. This scenario will
loop forever. Therefore, the server timeout should be smaller than the supplicant's EAPOL Start
frame retransmission rate.
2)
Overview of MAC-Based Authentication
Unlike 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
in 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 static entries into the
MAC Table. 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 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 do not 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, and only the MD5-Challenge method is supported.
802.1X and MAC-Based authentication configurations consist of two sections: system- and port-wide.
