I have two samba 4 AD DC running using the internal DNS. On one of them, DNS will fail after a short time (10-15 minutes). Restarting samba on this AD DC corrects the issue temporarily. This behavior started about 2 weeks ago. We had not made any changes to either system during this time so it is a complete mystery. I unfortunately used the latest version of samba from git (4.2) for creating these systems. I am in the process of building a new 4.1 server and will join it to the domain as an AD DC (hoping that this will work correctly). In /etc/krb5.conf, the server with failing dns is also listed as the admin_server for the realm. No idea what the effect of this is if I can point to the other server and still resolve dns. First though, what log files I should even be looking at for the DNS issues. I can run all the tests for a properly operating DNS and they all return the correct values (up until DNS fails). e.g. host -t SRV _ldap._tcp.ncs.k12.de.us host -t SRV _kerberos._udp.ncs.k12.de.us host -t A ncssamba1.ncs.k12.de.us all return correct information. kinit also works correctly, smbclient -L server -U% returns the correct information. I am running nslcd on both servers and that is also working. Completely lost on what to try to fix this dns issue. Sincerely, Dave Hopkins