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 IP 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 configuration as determined by the original RADIUS response remains unchanged and all such clients will have the same access as the authenticated 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.

This operation unblocks the port while an authenticated client session is in progress. In topologies where simultaneous, multiple client access is possible this can allow unauthorized and unauthenticated access by another client while an authenticated client is using the port. If you want to allow only authenticated clients on the port, then user-based access control should be used instead of port-based access control. Using the user-based method enables you to specify up to 32 authenticated clients. See 802.1X user-based access control.