Comtrol RocketLinx MP1204-XT, User Manual

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RocketLinx MP1204-XT User Guide : 2000644 Rev. A Configuration Pages - 81
Security | Network | NAS
Allow Guest VLAN
if EAPOL Seen
The MP1204-XT remembers if an EAPOL frame has been received on the port for
the life-time of the port. Once the MP1204-XT considers whether to enter the
Guest VLAN, it first checks to see if this option is enabled or disabled. If disabled
(unchecked; default), the MP1204-XT only enters the Guest VLAN if an EAPOL
frame has not been received on the port for the life-time of the port. If enabled
(checked), the MP1204-XT considers entering the Guest VLAN even if an EAPOL
frame has been received on the port for the life-time of the port.
The value can only be changed if the Guest VLAN option is globally enabled.
Port Configuration
Port The port number for which the configuration below applies.
Admin State
If NAS is globally enabled, this selection controls the ports authentication mode.
The following modes are available:
• Force Authorized
In this mode, the MP1204-XT sends one EAPOL Success frame when the port
link comes up, and any client on the port is allowed network access without
authentication.
• Force Unauthorized
In this mode, the MP1204-XT sends one EAPOL Failure frame when the port
link comes up, and any client on the port is disallowed network access.
• Port-based 802.1X
In the 802.1X-world, the user is called the supplicant, the MP1204-XT 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 MP1204-XT 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 supplicants 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 MP1204-XT) does not 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 MP1204-XT 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 never gets authenticated, because the
switch cancels on-going backend authentication server requests
whenever it receives a new EAPOL Start frame from the supplicant.
Since the server has not yet failed (because the X seconds have not
expired), the same server is contacted upon the next backend
authentication server request from the switch. This scenario loops
forever. Therefore, the server timeout should be smaller than the
supplicants EAPOL Start frame retransmission rate.
Item Configuration | Security | Network | NAS (Continued)