Configuring Port-Based and User-Based Access Control (802.1X)

Overview

This operation improves security by opening a given port only to individually authenticated clients, while simultaneously blocking access to the same port for clients that cannot be authenticated. All sessions must use the same untagged VLAN. Also, an authenticated client can use any tagged VLAN memberships statically configured on the port, provided the client is configured to use the tagged VLAN memberships available on the port. (Note that the session total includes any sessions begun by the Web Authentication or MAC Authentication features covered in chapter 3.) For more information, refer to “Option For Authenticator Ports: Configure Port-Security To Allow Only 802.1X-Authenticated Devices” on page 10-45.

802.1X Port-Based Access Control

802.1X port-based access control provides port-level security that allows LAN access only on ports where a single 802.1X-capable client (supplicant) has entered authorized RADIUS user credentials. For reasons outlined below, this option is recommended for applications where only one client at a time can connect to the port. Using this option, the port processes all traffic as if it comes from the same client. Thus, in a topology where multiple clients can connect to the same port at the same time:

■If the first client authenticates and opens the port, and then another client authenticates, the port responds as if the original client has initiated a reauthentication. With multiple clients authenticating on the port, the RADIUS configuration response to the latest client authentication replaces any other configuration from an earlier client authentication. If all clients use the same configuration this should not be a problem. But if the RADIUS server responds with different configurations for different clients, then the last client authenticated will effectively lock out any previously authenticated client. When any client to authenticate closes its session, the port will also close and remain so until another client successfully authenticates.

■The most recent client authentication determines the untagged VLAN membership for the port. Also, any client able to use the port can access any tagged VLAN memberships statically configured on the port, provided the client is configured to use the available, tagged VLAN memberships.

■If the first client authenticates and opens the port, and then one or more other clients connect without trying to authenticate, then the port config- uration as determined by the original RADIUS response remains unchanged and all such clients will have the same access as the authenti- cated client. When the authenticated client closes the session, the port will also be closed to any other, unauthenticated clients that may have also been using the port.

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