C
HAPTER
13
| Security Measures
Configuring 802.1X Port Authentication
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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 encryption
method used to pass authentication messages can be MD5 (Message-
Digest 5), TLS (Transport Layer Security), PEAP (Protected Extensible
Authentication Protocol), or TTLS (Tunneled Transport Layer Security). 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 allows the client to access the network. Otherwise,
non-EAP traffic on the port is blocked or assigned to a guest VLAN based on
the “intrusion-action” setting. In “multi-host” mode, only one host
connected to a port needs to pass authentication for all other hosts to be
granted network access. Similarly, a port can become unauthorized for all
hosts if one attached host fails re-authentication or sends an EAPOL logoff
message.
Figure 213: Configuring Port Security
The operation of 802.1X on the switch requires the following:
◆ The switch must have an IP address assigned.
◆ RADIUS authentication must be enabled on the switch and the IP
address of the RADIUS server specified.
◆ 802.1X must be enabled globally for the switch.
◆ Each switch port that will be used must be set to dot1X “Auto” mode.
◆ Each client that needs to be authenticated must have dot1X client
software installed and properly configured.
◆ The RADIUS server and 802.1X client support EAP. (The switch only
supports EAPOL in order to pass the EAP packets from the server to the
client.)
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.
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