Authentication is used to check whether the identity of the user who attempts to access the network is valid. Authorization is used to specify the network access rights that an authorized user can have, that is, the resources that the authorized user can access. ACLs and UCL groups are often used for authorization. RADIUS authorization is used as an example. For details about other authorization methods and more authorization parameters, see AAA Authorization Scheme.
After a user is authenticated, the authentication server assigns an ACL to the user. Then, the access device controls the user packets according to the ACL.
A free rule allows users to obtain certain network access rights before they are authenticated, to meet basic network access requirements.
You can configure either a common free rule or an ACL-defined free rule. A common free rule is determined by parameters such as the IP address, MAC address, interface, and VLAN, while an ACL-defined free rule is determined by ACL rules. Both the rules can specify the destination IP address that users can access before being authenticated. An ACL-based free rule can also define the name of a destination domain that users can access before being authenticated.
Sometimes, defining a free rule by domain name is simpler and more convenient than defining a free rule by IP address. This is because a domain name is easier to remember. For example, some users who do not have an authentication account must first log in to the official website of a carrier and apply for a member account, or log in using a third-party account such as a Twitter or Facebook account. In this case, you can configure ACL-defined free rules to specify domain names of the websites that users can access before they are authenticated.