Standard mode authentication means that a user can only authenticate against LDAP, if an LDAP server is defined and active. Mixed mode authentication means that a user can login with either LDAP or local credentials. If a user is known on an LDAP server, but the credentials are incorrect, access is denied.
Standard mode authentication is enabled when at least one LDAP server is active. Each defined LDAP server is checked to determine if a user (with specific user name and password) can be authenticated. Access is granted when authentication succeeds on one of the servers.
When no LDAP server is defined, users will only be able to login with local credentials. If at least one LDAP server is active and a user account is set to use mixed mode authentication, each defined LDAP server is checked to determine if a user (with specific user name and password) can be authenticated. If the user is unknown on all defined LDAP servers, then local database authentication is attempted. Access is denied when a user is also unknown based on local credentials. If a user is known on an LDAP server, but the credentials are incorrect, access is denied.