TACACS+ (Terminal Access Controller Access-Control System Plus) is a Cisco proprietary protocol which provides access control for routers, network access servers and other networked computing devices via one or more centralized servers. TACACS+ uses port tcp 49 and provides separate authentication, authorization and accounting services.

Below shows you the general steps involved,

First of all configure you router to use TACACS+. Make sure that you do not logout of the router at the point of running the command aaa new-model. This command clears your current login settings, so if you logout you will not have the configuration in place to allow you to log back in.

(config)# aaa new-model 
(config)# tacacs-server host [tacacs ip] single-connection
(config)# tacacs-server host [tacacs ip] key [key]

(config)# aaa authentication login [AUTH LIST NAME] group tacacs+ local  
(config-line)# line vty 0 4 
(config-line)# login authentication [AUTH LIST NAME]