SSH

ACS

RADIUS

TACACS+

I prefer not to answer.

TACACS+ uses UDP port 1645 or 1812 for authentication, and UDP port 1646 or 1813 for accounting.

TACACS+ is an open IETF standard.

TACACS+ provides authorization of router commands on a per-user or per-group basis.

I prefer not to answer

TACACS+ is backward compatible with TACACS and XTACACS.

AAA authorization is not configured.

I prefer not to answer.

The wrong vty lines are configured.

The administrator has used the wrong password.

The administrator does not have enough rights on the PC that is being used.