[Samba] Synology NAS looses connection to Samba AD

[Alexander Harm]

We have to Samba DCs and a couple of Synology NAS connected/bound to the Samba AD. On regular basis the Synology NAS (I believe Samba 4.4.16) looses its connection to the AD outputting the error message, that the domain cannot be found. In the logs of the NAS I can only find the error message “synowin: domain_test_join.c:59 net ads test join fail”.

In the logs of the DC I notice that from one second to the other the connection seems to fail:

[2020/03/18 00:51:45.001044, 3] ../../auth/auth_log.c:653(log_authentication_event_human_readable) Auth: [Kerberos KDC,ENC-TS Pre-authentication] user [(null)][FILESERVER$@DS.EXAMPLE.COM] at [Wed, 18 Mar 2020 00:51:45.001031 CET] with [aes256-cts-hmac-sha1–96] status [NT_STATUS_OK] workstation [(null)] remote host [ipv4:10.0.1.100:51352] became [EXAMPLE][FILESERVER$] [S–1–5–21–1451753080–565542361–3466525082–2103]. local host [NULL][2020/03/18 00:53:49.362120, 2] ../../auth/auth_log.c:653(log_authentication_event_human_readable) Auth: [Kerberos KDC,ENC-TS Pre-authentication] user [(null)][FILESERVER$@DS.EXAMPLE.COM] at [Wed, 18 Mar 2020 00:53:49.362103 CET] with [aes256-cts-hmac-sha1–96] status [NT_STATUS_WRONG_PASSWORD] workstation [(null)] remote host [ipv4:10.0.1.100:51393] mapped to [EXAMPLE][FILESERVER$]. local host [NULL]

Can anyone explain to me what happens and how to fix this?

Thanks a lot,

Alexander