Our office subnet is 10.1.10.0/24.
I have a gateway (10.1.10.1) that is forwarding DNS requests to a server running DNSmasq (10.1.10.2). I have an IPsec tunnel to our Parent Company's network (10.2.2.0/24).
In the resolv.conf on 10.1.10.2, I've specified two (2) nameservers, 18.104.22.168 (Google DNS) and 10.2.2.2 (Parent Company DNS).
My issue is that 10.2.2.2 also services another 10.1.10.0/24.
This means that sometimes reverse DNS lookups return hostnames on the foreign 10.1.10.0/24 instead of our internal network. We can see this by using tools like dig or IP scanners. Also, sometimes our OS X bash prompts show the wrong hostname.
So my proposed solution would be to direct all reverse DNS lookups for addresses within 10.1.10.0/24 to 10.1.10.2's internal lookup table, but I don't know how to go about this, or if this is the right solution.
I should note that I have no control over 10.2.2.2.
EDIT: I have found another possible solution. I'll test it out before adding it as an answer. Assuming 10.1.10.1 uses DNSmasq, I can add specify the --bogus-priv option. Since 10.1.10.1 is also our DHCP server, it should return "no such domain" for any reverse DNS queries of hosts within 10.1.10.0/24 that are not within the DHCP leases file.