• Create a "user" locally on the Digi CM via the web ui or configmenu.
  
• Have this same user in your remote authentication database (RADIUS, TACACS+, LDAP, Kerberos).
  
• Assign the user locally to a different password than what you have in your remote authentication database.
  
• Login using the password assigned in your remote database.
  

NOTE: Remote authentication is only supported for "users", "admins" (root, admin) can only be authenticated locally.