ldap authetication not working

I have extracted the ldap plugin and also activated it.After which i started to get the LDAP option .I have put my ldap server ip into the ldap settings .I have already made account of some of the ldap users.

But still the ldap is not authenticating the user of ldap.Can you pls. help me as to what more needs to be made to make it work.Do i need to also make some code changes