[Samba] Conflict entries in DNS with DHCP and dynamic DNS updates 

Norbert Hanke norbert.hanke at gmx.ch
Fri Feb 19 22:30:31 UTC 2021

I have the same here with isc-dhcpd-4.4.1 on Debian/RapsberryOS.

I think it's is a bug in the ISC DHCP server when it runs in failover
pair mode:

Whenever a node asks for a lease and that node is already known to both
DHCP servers then both send a response (luckily the same response), and
as a consequence both DHCP servers send an update do DNS.

If a node with a still unknown MAC address asks for a lease the very
first time then only one of the two servers responds.

Do you see the same behaviour?


On 18.02.2021 19:16, Samba Fan via samba wrote:
> It is about DNS updates through the ISC DHCP server failover cluster in a Samba 4 Active Directory environment. I have implemented this as described in the Samba wiki (https://wiki.samba.org/index.php/Configure_DHCP_to_update_DNS_records_with_BIND9).
> The failover works fine from the outside. However, the script (I use version 0.9.2) is executed on both servers at the same time (event "on commit"). This has the effect that a DNS record is created on both servers at the same time, if it did not already exist. This creates "conflict records" in both the forward and reverse zones, which the DNS then resolves so that one of them appears as hostname\nCNF:UID or ip-address\nCNF:UID in the forward zone or reverse zone, respectively.
> The name resolution in both directions works, because the correct entries are in the DNS. However, the "useless" CNF entries remain. What can I set or check? How can I prevent these CNF entries? I have not found an answer yet.
> These are the operating systems and versions of the software packages involved:
> Server operating system: Ubuntu 16.04.7 LTS
> Samba: Version 4.3.11-Ubuntu
> DNS: BIND 9.10.3-P4-Ubuntu
> DHCP: ISC DHCP Server version 4.3.3
> Operating system of DHCP clients: Windows 10 1909 (DHCP updates by clients are disabled)
> Regards, Sambafan
> P

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