Hi Valentin,
I’m guessing your master is a samba4 ad dc.
If so samba is interfering with your desired dns settings by automatically re-adding the dns entries.
You can try to exclude the second interface by adding it to the ucr variable “samba/register/exclude/interfaces”
(don’t forget to restart samba afterwards by executing “service samba restart”)
If you remove the dns entries they shouldn’t reappear.
Regards,
Gronkdalonka