[Samba] Samba 4.7.4 DC replicating to itself?

[Norbert Hanke]

Hi Samba Experts,

I have a small AD setup with two Samba DCs, both running Samba 4.7.4.

Since a few days, one of the DCs appears to replicate to itself.
|
On the affected DC2, "samba-tool drs showrepl" displays the 5 usual 
directory nodes that are replicated:|
|   Default-First-Site-Name\DC2|
|||DSA Options: 0x00000001|
|||DSA object GUID: 8acfcfcd-6d87-4fee-8dfd-d1c111fdb821|
|||DSA invocationId: c56a924e-e3c7-4486-b94a-fa39046f760f|
||||
|||==== INBOUND NEIGHBORS ====|
||||
|||DC=ad,DC=mydomain,DC=ch|
|||        Default-First-Site-Name\DC1 via RPC|
|||                DSA object GUID: bdb72655-0b22-4d55-b9c1-62015af4bfd7|
|||                Last attempt @ Sun Feb 25 16:12:41 2018 UTC was 
successful|
|||                0 consecutive failure(s).|
|||                Last success @ Sun Feb 25 16:12:41 2018 UTC|
|||and so on, the same for|
||||||DC=ForestDnsZones,DC=ad,DC=mydomain,DC=ch
||||||||CN=Schema,CN=Configuration,DC=ad,DC=mydomain,DC=ch
||||||||CN=Configuration,DC=ad,DC=mydomain,DC=ch
    DC=DomainDnsZones,DC=ad,DC=mydomain,DC=ch||

and it displays
||||DC=ForestDnsZones,DC=ad,DC=mydomain,DC=ch
||||Default-First-Site-Name\DC2 via RPC
||||                DSA object GUID: 8acfcfcd-6d87-4fee-8dfd-d1c111fdb821
||||                Last attempt @ Sun Feb 25 16:12:35 2018 UTC was 
successful
||||                0 consecutive failure(s).
||||                Last success @ Sun Feb 25 16:12:35 2018 UTC
||||and
||||DC=DomainDnsZones,DC=ad,DC=mydomain,DC=ch
||||Default-First-Site-Name\DC2 via RPC
||||                DSA object GUID: 8acfcfcd-6d87-4fee-8dfd-d1c111fdb821
||||                Last attempt @ Sun Feb 25 16:12:39 2018 UTC was 
successful
||||                0 consecutive failure(s).
||||                Last success @ Sun Feb 25 16:12:39 2018 UTC
i.e. this system apparently replicates to itself.

What's wrong with DC2? Beside this strange output it appears to work 
correctly.DC1 does not show this behaviour.

Regards,
Norbert