Using useradd for LDAP user account!

I read the useradd man page and saw the '-D' argument for binding to LDAP. I am trying to use it to add user accounts to our LDAP server but it doesn't do anything! The man page states that if you use '-D' it should ask for the LDAP password and it doesn't, it creates the account locally on the server (not in LDAP). Maybe I am using the incorrect settings, here is the actual command that I used: useradd -D cn=admin,dc=example,dc=edu \ -c "Some User" -d /home/students/username \ -g students -s /bin/bash username Thanks in advance.