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encapsulates the EAP part of the frame into the relevant type (EAPOL or RADIUS) and forwards it.
When authentication is complete, the RADIUS server sends a special packet containing a success or failure
indication. Besides forwarding this decision to the supplicant, the switch uses it to open up or block traffic on
the switch port connected to the supplicant.
Note:
Suppose two backend servers are enabled and that the server timeout is configured to X seconds
(using the AAA configuration page), and suppose that the first server in the list is currently down (but not
considered dead). Now, if the supplicant retransmits EAPOL Start frames at a rate faster than X seconds, then
it will never get authenticated, because the switch will cancel on-going backend authentication server
requests whenever it receives a new EAPOL Start frame from the supplicant. And since the server hasn't yet
failed (because the X seconds haven't expired), the same server will be contacted upon the next backend
authentication server request from the switch. This scenario will loop forever. Therefore, the server timeout
should be smaller than the supplicant's EAPOL Start frame retransmission rate.
MAC-based Auth.
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 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 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.
Port State
The current state of the port. It can undertake one of the following values:
Globally Disabled:
NAS is globally disabled.
Link Down:
NAS is globally enabled, but there is no link on the port.
Authorized:
The port is in Force Authorized or a single-supplicant mode and the supplicant is authorized.
Unauthorized:
The port is in Force Unauthorized or a single-supplicant mode and the supplicant is not
successfully authorized by the RADIUS server.
X Auth/Y Unauth:
The port is in a multi-supplicant mode. Currently X clients are authorized and Y are
unauthorized.
Restart
Two buttons are available for each row. The buttons are only enabled when authentication is globally
enabled and the port's Admin State is in an EAPOL-based or MAC-basedmode.
Clicking these buttons will not cause settings changed on the page to take effect.
Reauthenticate:
Schedules a reauthentication whenever the quiet-period of the port runs out (EAPOL-based
authentication). For MAC-based authentication, reauthentication will be attempted immediately.
The button only has effect for successfully authenticated clients on the port and will not cause the clients to
get temporarily unauthorized.
Reinitialize:
Forces a reinitialization of the clients on the port and thereby a reauthentication immediately.
The clients will transfer to the unauthorized state while the reauthentication is in progress.
