Optical Systems Design OSD2524, User Manual

Page: 94 / 402

OPTICAL SYSTEMS DESIGN
DOC ID: 10120001
OSD2524 OPERATOR MANUAL
PAGE 94
Allow Guest VLAN if EAPOL Seen
The switch remembers if an EAPOL frame has been received on the port for the life-time of the port.
Once the switch considers whether to enter the Guest VLAN, it will first check if this option is enabled or
disabled. If disabled (unchecked; default), the switch will only enter 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 switch will
consider 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
The table has one row for each port on the switch and a number of columns, which are:
Port
The port number for which the configuration below applies.
Admin State
If NAS is globally enabled, this selection controls the port's authentication mode. The following modes
are available:
FORCE AUTHORIZED
In this mode, the switch will send one EAPOL Success frame when the port link comes up, and any client
on the port will be allowed network access without authentication.
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