Redmine

i have a LDAP server and its has a group called .

cn=internal ou=group,dc=example,dc=com

--users of this group is :

uid=user1,ou=staff,dc=example,dc=com
uid=user2,ou=staff,dc=example,dc=com

i need to only authenticate the users under cn=internal ....

is it possible to achive that in redmine

LDAP search for the cn=internal group as follows ,

dn: cn=internal,ou=group,dc=example,dc=com
objectClass: groupOfNames
objectClass: top
cn: internal
member: uid=user1,ou=user,dc=example,dc=com
member: uid=user1,ou=user,dc=example,dc=com

in redmine 2.1.2 there is ldap filter field , so i filled it as

(&(objectClass=inetOrgPerson)(memberOf=cn=internal,ou=group,dc=example,dc=com))

Redmine syays "LDAP filter is invalid" ,

Can some expert help with this issue ...?

Thank in advance