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Cisco IE 2000 Switch Software Configuration Guide
OL-25866-01
Chapter 12 Configuring Switch-Based Authentication
Information About Configuring Switch-Based Authentication
CoA Session Reauthentication
The AAA server typically generates a session reauthentication request when a host with an unknown
identity or posture joins the network and is associated with a restricted access authorization profile (such
as a guest VLAN). A reauthentication request allows the host to be placed in the appropriate
authorization group when its credentials are known.
To initiate session authentication, the AAA server sends a standard CoA-Request message which
contains a Cisco vendor-specific attribute (VSA) in this form:
Cisco:Avpair=“subscriber:command=reauthenticate” and one or more session identification attributes.
The current session state determines the switch response to the message. If the session is currently
authenticated by IEEE 802.1x, the switch responds by sending an Extensible Authentication Protocol
over LAN (EAPoL) RequestId message to the server.
If the session is currently authenticated by MAC authentication bypass (MAB), the switch sends an
access-request to the server, passing the same identity attributes used for the initial successful
authentication.
If session authentication is in progress when the switch receives the command, the switch terminates the
process, and restarts the authentication sequence, starting with the method configured to be attempted
first.
If the session is not yet authorized, or is authorized via guest VLAN, or critical VLAN, or similar
policies, the reauthentication message restarts the access control methods, beginning with the method
configured to be attempted first. The current authorization of the session is maintained until the
reauthentication leads to a different authorization result.
CoA Session Termination
There are three types of CoA requests that can trigger session termination. A CoA Disconnect-Request
terminates the session, without disabling the host port. This command causes reinitialization of the
authenticator state machine for the specified host, but does not restrict that host’s access to the network.
To restrict a host’s access to the network, use a CoA Request with the
Cisco:Avpair="subscriber:command=disable-host-port" VSA. This command is useful when a host is
known to be causing problems on the network, and you need to immediate ly block network access for
the host. When you want to restore network access on the port, re enable it using a non-RADIUS
mechanism.
When a device with no supplicant, such as a printer, needs to acquire a new IP address (for example,
after a VLAN change), terminate the session on the host port with port-bounce (temporarily disable and
then reenable the port).
CoA Disconnect-Request
This command is a standard Disconnect-Request. Because this command is session-oriented, it must be
accompanied by one or more of the session identification attributes described in the “CoA Session
Identification” section on page 12-11. If the session cannot be located, the switch returns a
Disconnect-NAK message with the “Session Context Not Found” error-code attri bute. If the session is
located, the switch terminates the session. After the session has been completely removed, the switch
returns a Disconnect-ACK.
If the switch fails-over to a standby switch before returning a Disconnect-ACK to the client, the process
is repeated on the new active switch when the request is resent from the client. If the sessi on is not found
following resend, a Disconnect-ACK is sent with the “Session Context Not Found” error-code attribute.