[Samba] Join an additional Samba DC to an existing Active Directory

[basti]

Hello,
I try to add a BDC to my AD using this Howto
https://wiki.samba.org/index.php/Join_an_additional_Samba_DC_to_an_existing_Active_Directory#Preparing_the_host_for_the_domain_join

host -t A pdc.kes.local
pdc.kes.local has address 192.168.122.2

ldapsearch -h pdc.kes.local -b'dc=kes,dc=local' -x
# extended LDIF
#
# LDAPv3
# base <dc=kes,dc=local> with scope subtree
# filter: (objectclass=*)
# requesting: ALL
#

# kes.local
dn: dc=kes,dc=local
objectClass: top
objectClass: dcObject
objectClass: organization
o: kes.local
dc: kes

...

but when I try

samba-tool domain join kes.local DC -Uadministrator --realm=KES.local
--dns-backend=SAMBA_INTERNAL
Finding a writeable DC for domain 'kes.local'
Found DC pdc.kes.local
Failed to bind - LDAP client internal error: NT code 0x80090302
Failed to connect to 'ldap://pdc.kes.local' with backend 'ldap': (null)
ERROR(ldb): uncaught exception - None
  File "/usr/lib/python2.7/dist-packages/samba/netcmd/__init__.py", line
175, in _run
    return self.run(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/samba/netcmd/domain.py", line
657, in run
    dns_backend=dns_backend)
  File "/usr/lib/python2.7/dist-packages/samba/join.py", line 1116, in
join_RODC
    machinepass, use_ntvfs, dns_backend, promote_existing)
  File "/usr/lib/python2.7/dist-packages/samba/join.py", line 85, in
__init__
    credentials=ctx.creds, lp=ctx.lp)
  File "/usr/lib/python2.7/dist-packages/samba/samdb.py", line 57, in
__init__
    options=options)
  File "/usr/lib/python2.7/dist-packages/samba/__init__.py", line 115,
in __init__
    self.connect(url, flags, options)
  File "/usr/lib/python2.7/dist-packages/samba/samdb.py", line 72, in
connect
    options=options)
root at rtr:/home/user# man samba-tool

On my pdc I use BIND aus DNS backend.

Thanks for any support.
Best Regards