C
ONFIGURING

THE

S

WITCH

3-88

Configuring 802.1X Port Authentication

Network switches can provide open and easy access to network resources
by simply attaching a client PC. Although this automatic configuration and
access is a desirable feature, it also allows unauthorized personnel to easily
intrude and possibly gain access to sensitive network data.
The IEEE 802.1X (dot1x) standard defines a port-based access control
procedure that prevents unauthorized access to a network by requiring
users to first submit credentials for authentication. Access to all switch
ports in a network can be centrally controlled from a server, which means
that authorized users can use the same credentials for authentication from
any point within the network.
This switch uses the
Extensible
Authentication
Protocol over LANs
(EAPOL) to exchange
authentication
protocol messages
with the client, and a
remote RADIUS
authentication server
to verify user identity and access rights. When a client (i.e., Supplicant)
connects to a switch port, the switch (i.e., Authenticator) responds with an
EAPOL identity request. The client provides its identity (such as a user
name) in an EAPOL response to the switch, which it forwards to the
RADIUS server. The RADIUS server verifies the client identity and sends
an access challenge back to the client. The EAP packet from the RADIUS
server contains not only the challenge, but the authentication method to be
used. The client can reject the authentication method and request another,
depending on the configuration of the client software and the RADIUS
server. The authentication method must be MD5. The client responds to
the appropriate method with its credentials, such as a password or
certificate. The RADIUS server verifies the client credentials and responds
with an accept or reject packet. If authentication is successful, the switch
802.1x
client
RADIUS
server
1. Client attempts to access a switch port.
2. Switch sends client an identity request.
3. Client sends back identity information.
4. Switch forwards this to authentication server.
5. Authentication server challenges client.
6. Client responds with proper credentials.
7. Authentication server approves access.
8. Switch grants client access to this port.