Authentication, Authorization, Accounting

AAA is an important feature in networking. AAA stands for Authentication, Authorization and Accounting.

Authentication basically asks users for passwords. It can be done using an internal database of the server/router or it can be done remotely using a RADIUS server (UDP service) or TACACS+ server (TCP service) in order to control users from accessing the network.

To configure AAA service type the "aaa new-model" in the configuration terminal mode. To define RADIUS location type radius-server host "" in the configuration terminal mode. TO define TACACS+ location type "tacacs-server host " in the configuration terminal mode. To apply AAA login type "line vty 0 15" then "login authentication default" also in the configuration terminal mode.

Authorization is used to give permissions to do something on the router or switch configuration. It creates user profiles and determines who can do what. The configuration is "aaa authorization" in the configure terminal mode.

Accounting is used to track users or customers activity. This can be also used to bill customers for their usage of the network.

That is a little bit of the AAA explanation.