I finally found my mistake and fixed it that way.
thank you for the help.

require 'net/ldap'

# look up Machine to ProdWindowsXPWorkstations
 ldap = Net::LDAP.new :host => '11111111',
      :port => 389,
      :auth => {
            :method => :simple,
            :username =>
"cn=user,ou=ou0,ou=ou1,ou=ou3,dc=dc,dc=dc1,dc=net",
            :password => "pass"
      }

 filter = Net::LDAP::Filter.eq( "cn", "monnomdemachine" )
 treebase = "dc=dc,dc=dc1,dc=net"

 ldap.search( :base => treebase, :filter => filter ) do |entry|
   dnwks = "DN: #{entry.dn}"


    dn = "CN=mygoupe,OU=uu2,OU=uu1,OU=uu,dc=dc,dc=dc1,dc=net"
 ldap.add_attribute dn, :member, dnwks
end
p ldap.get_operation_result

-- 
Posted via http://www.ruby-forum.com/.