no logging rate-limit: if you are using rate-limit and u have enbaled syslog logging , this will avoid generating syslog messages when rate-limit speed limit has reached , This line seems to be spare
aaa new-model : This command will enable the AAA : Its critical
aaa authentication login default group tacacs+ local : Your configurtaion shows that you are using a TACACS server , so this will line will check the login facility on the router. Actually when u type "Enable" which will lead you to the privilage mode this line is working : Critical
aaa authentication login no_tacacs enable : Seems to be spare
aaa authentication login data none : seems to be spare
aaa authentication ppp default group tacacs+ : This will check the dialin users authentication : Critical
aaa authentication ppp defalt if-needed group tacacs+ local : EXTRA LINE
aaa authentication ppp data none : EXTRA LINE
aaa authorization exec default group tacacs+ local : This will specify TACAS to check every command that you enter and authorize you
aaa authorization network default group tacacs+ local : This will authorize the PPP Dial-in Users
aaa accounting nested : Extra Line
aaa accounting update newinfo : Change this to priodic
aaa accounting exec default start-stop group tacacs+ : How accounting information will be send to the Accounting software about any command that you type: If you like to have log of what you do , enable this
aaa accounting network default start-stop group tacacs+ : This determines how the ppp dial-in users accounting infomation is sent to accounting software : Critical
enable secret 5 $1$Mnfl$0CIzepuR6rRS6MTGpbWMX. :If router wont be able to communicate with TACACS Server will use this password will let you log-in