Need information to bypass the preauth in openssh

[Vishwanath KC]

Hi,

I am Vishwanath, I got one requirement from our clients regarding remote
authentication. In which all users info present in remote user database.

Currently using openssh for SSH connections.
To open a new remote session via SSH, the openssh will look into the
/etc/passwd file. If user present then it will allow to login using
password or key authentication.

But in my case all user info is present in remote database and
authentication is form remote using tacacs+ server.

Due to this I am facing error message as below
2017 Jan 13 10:45:51 : switch : sshd :  Invalid user test from 10.12.16.16
2017 Jan 13 10:45:51 : switch :  input_userauth_request: invalid user test
[preauth]

Please give some inputs on how to handle this scenario.

Regards,
Vishwanath KC
+918892599848.