can't contact LDAP server

[Frank Zhang <fzhang@hsc.unt.edu>]

I set up LDAP server on Red Hat Linux
I have two Red Hat Linux machine A and machine B
machine A:
  LDAP server: openldap 2.1
  when I ran "ldapsearch -x -b 'dc=example,dc=com' on machine A,  it is
working

On machine B:
   when I ran "ldapsearch -x -b 'dc=example,dc=com' -h MachineA -d 1
I got error message:
   ......
   ldap_is_socket_ready:error on socket 3: errno: 113 ( no route to host)
   can't contat LDAP server

The firewall on both LINUX servers are wide open.
Can you point the direction for me : where is wrong ?
Thank you very much
Frank Zhang