Alloy AS5010-P, User Manual

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AS Series User Manual
93
Doc No.: AS5-0116-01
Force
Unauthorized In this mode, the switch will send one EAPOL Failure frame when the port link
comes up, and any client on the port will be disallowed network access.
Port-based 802.1X In the 802.1X-world, the user is called the supplicant, the switch is the
authenticator, and the RADIUS server is the authentication server. The
authenticator acts as the man-in-the-middle, forwarding requests and
responses between the supplicant and the authentication server. Frames sent
between the supplicant and the switch are special 802.1X frames, known as
EAPOL (EAP over LANs) frames. EAPOL frames encapsulate EAP PDUs
(RFC3748). Frames sent between the switch and the RADIUS server are RADIUS
packets. RADIUS packets also encapsulate EAP PDUs together with other
attributes like the switch's IP address, name, and the supplicant's port number
on the switch. EAP is very flexible, in that it allows for different authentication
methods, like MD5-Challenge, PEAP, and TLS. The important thing is that the
authenticator (the switch) doesn't need to know which authentication method
the supplicant and the authentication server are using, or how many
information exchange frames are needed for a particular method. The switch
simply 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.
Single 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 Single 802.1X variant. Single 802.1X is really not an IEEE