# Tunnel Subscriber Authentication Configuration Overview

When a AAA domain map includes any tunnel configuration, users in this domain are considered to be tunnel subscribers. By default, any such subscriber is granted access without being authenticated by the authentication server. Access is granted even when the user provides an invalid username and password. The tunnel configuration for the subscriber comes from the AAA domain map.

For example, if the authentication protocol for a AAA domain map is RADIUS, AAA grants access to subscribers from this domain immediately without sending access requests to the configured RADIUS server. Because of this behavior, these subscribers cannot get any additional control attributes from the authentication server. This reduces your ability to manage the tunnel subscribers.

In this default situation, if you want the domain subscribers to be managed by the authentication server for any control attribute, then that domain map cannot have any tunnel configuration. Typically, this means you must configure the subscriber individually.

You can use the tunnel-subscriber authentication command to get around this limitation. When you enable authentication with this command, access requests for the tunnel subscribers in the domain are sent to the configured authentication server. When the access replies from authentication server are processed, various user attributes from the server can be applied to the subscribers.

When the authentication server returns tunnel attributes, these returned values take precedence over the corresponding local tunnel configuration values in the AAA domain map. If the server does not return any tunnel attributes, then the tunnel subscriber’s tunnel settings are configured according to the domain map’s tunnel settings.

If the authentication server returns a redirect VSA and the corresponding AAA domain map has local tunnel configurations, the VSA is ignored. Access is denied to the user when the authentication server rejects the access request.

The tunnel-subscriber authentication command has no effect on subscribers in a domain with no tunnel configuration. When a AAA domain map has no tunnel configuration, subscribers in the domain are authenticated by the authentication server. If the server grants access, then the subscribers get their tunnel settings only from the authentication server.

By default, tunnel subscribers in the domain are granted access with no external authentication. Use the enable keyword to enable authentication. Use the disable keyword to restore disable user authentication.

To configure authentication of tunnel subscribers within a AAA domain by an external authentication server.

- Example
  host1(config-domain-map)#tunnel-subscriber authentication enable

#### Related Documentation

- Overview of Mapping a User Domain to a Virtual Router
- tunnel-subscriber authentication