Dear Douglas,
enable secret is to allow ingress to Privilege 15 mode and not global configuration mode. So if you use TACACS,
1) Is the enable secret required ?
Well, Enable Secret is not required to login if you have a privilege 15 username password configured.
username douglas priviledge 15 password barboza
Because using the above username you will be placed directly in to the Privilege mode.
2) . the authentication could do it trough server ?
aaa new-model
aaa authentication login default group tacacs+ local
The above configuration means that in order to login in to the router, use the TACACS for authentication. And If TACACS is not reachable, then use the local database to login.
An additional info 4 u. Look at the following command,
aaa authentication enable default group tacacs+ enable
This command is optional and which means that in order to get in to the privilege mode from user Exec mode, use TACACS for authentication, else use the local "enable password/secret".
But, since we have used a priv 15 username password in our local database, we dont need the enable password/secret.
3) Yes Douglas, you are right ,!! a level 15 local credential substitute the requirement of a enable secret ..
Hope this helps..
Narendrakumar B
Please do not forget to rate the useful posts.!!
