[Samba] Secondary Nameserver not working

[Mark Foley]

I've configured a secondary slave nameserver based on what I consider rather expert advice, but
it's not working as expected. I'm trying to determine if I've done something wrong with basic
configuration or if there are AD/DC nuances afoot.

The main nameserver is the domain Active Directory/Domain Controller running Samba 4.4.16 on
Slackware64 14.2. This has been running for a few years w/o problem. It's domain IP is
192.168.0.2.

I've attempted to configure a DNS slave on another Linux Slackware64 14.2 system, IP 192.168.0.3.
This host is on the domain LAN, but is not a domain member.

When bind is running on the slave, the zone files are updated as expected. Both Windows and
Linux domain members show both 192.168.0.2 and 192.168.0.3 as nameservers. However, when
192.168.0.2 goes offline, the domain members can no longer access the Internet. That condition
persists until 192.168.0.2 comes back on line. So, the slave DNS server is not working correctly.

In 192.168.0.2 has "allow-transfer { 192.168.0.3; };" set in named.conf options, and in zone and
reverse zone files.

Below is the named.conf on the slave. Am I doing something wrong AD/DC-wise?

options {
        directory "/var/named";

        forwarders {            // These are the ISP provided name servers
           209.18.47.61;
           209.18.47.62;
        };

        allow-query { any; };
        allow-recursion {192.168.0.0/24;};
};

logging{
  channel marks_log {
    syslog local7;
    severity info;
  };
  category default {
    marks_log;
  };
};

zone "hprs.local" IN {
        type slave;
        masters { 192.168.0.2; };
        file "/var/named/db.hprs.local";
};

zone "0.168.192.in-addr.arpa" IN {
    type slave;
    masters { 192.168.0.2; };
    file "/var/named/db.192.168.0";
};