How to Configure a Predefined Authentication Order

Benefits of Configuring Multiple Authentication Methods

• Enhances network security by attempting multiple authentication methods before restricting client access, ensuring thorough verification of client legitimacy.

• Improves user experience by reducing unnecessary placement of clients into server-reject VLANs, allowing for alternative authentication methods to grant access.

• Increases flexibility in network access control by allowing configurable authentication sequences that adapt to different network policies and requirements.

• Ensures optimal use of network resources by preventing immediate client isolation, thus allowing for more efficient handling of authentication processes.

• Supports a resilient authentication workflow that maintains a balance between security and accessibility, even in re-authentication scenarios.

Overview

The Dot1x Selective Server-Reject VLAN feature significantly enhances the 802.1X client authentication mechanism by modifying how clients are handled upon authentication rejection by a RADIUS server. Instead of immediately placing rejected clients into a server-reject VLAN, the switch attempts other configured authentication methods, such as MAC RADIUS. This approach ensures a thorough verification process, potentially allowing clients to gain network access through alternative authentication paths before resorting to restrictive measures.

To utilize this feature, you must carefully configure the authentication order and the server-reject VLAN settings. The authentication order dictates the sequence in which the switch attempts different methods, ensuring that all potential avenues for client authentication are explored. For instance, you can set the order to try 802.1X first, followed by MAC RADIUS, depending on your network policies and requirements. The feature requires that the post-auth-order option be enabled on the interface, which directs the switch to try additional authentication methods before placing the client into the server-reject VLAN.

The CLI command set protocols dot1x authenticator interface <INTF_NAME> server-reject-vlan post-auth-order is central to configuring this feature. This command ensures that the switch attempts all configured authentication methods in the specified order before enforcing the server-reject VLAN. Note that this feature is not compatible with captive portal configurations on the same interface and requires that MAC RADIUS be configured. During re-authentication, the feature maintains a balance between flexibility and security by placing clients directly into the server-reject VLAN if the RADIUS server rejects them again, thus preventing potential security loopholes.

Configuration Example

To implement the Dot1x Selective Server-Reject VLAN feature, consider the following configuration example. Assume you have an interface that needs to support both 802.1X and MAC RADIUS authentication methods, and you want to ensure clients are given multiple chances to authenticate before being placed in the server-reject VLAN.

Configure MAC RADIUS and Dot1x on the Interface:

set protocols dot1x authenticator interface ge-0/0/1 mac-radius set protocols dot1x authenticator interface ge-0/0/1

Set the Authentication Order:

set protocols dot1x authenticator interface ge-0/0/1 server-reject-vlan post-auth-order

Specify the Server-Reject VLAN:

set protocols dot1x authenticator interface ge-0/0/1 server-reject-vlan vlan10

In this example, the switch first tries 802.1X authentication. If the RADIUS server rejects the client, the switch then attempts MAC RADIUS authentication. Only if both methods fail will the client be placed in VLAN 10, the server-reject VLAN. This configuration ensures a flexible and secure authentication process, improving the overall network user experience.