The set-up: We have two external networks we can connect too The internet (1) and a external private Intranet (2)
The Clause: Both external networks have DNS Servers available but neither networks can resolve each others network, however some "services" are found on both networks which can issue different content
The issues: In a domain environment if we set the AD DNS forwarders to the External intranet we cant get the internet to resolve i.e where is www.google.com? if we set the first forwarder to the internet i.e opendns, we can then get www.google.com but we couldn't then get abc.website.net. If we manually add zones to the DNS we then have to fill in all the .net(s) sites which is impossible!.
So the resolution to this was to set the host file on each client with the information of all the sites we could look at on the external intranet, this works and resolves all issues, but..
The next issue has now occurred where by a mobile device user can leave the the domain and access the external intranet via VPN but the IP address locations change, due to the host file statically setting the IP's this overrides the DNS servers on that network, and then causes connectivity issues.
One other work around I have thought of, is where by we segregate the domain network via vlans and run two dhcp on different Nic's thus setting a different DNS sever via the DHCP Where we statically set the zones for those clients who will leave the building and use a VPN and remove the host file, thus when outside of the building the other DNS settings will work when the VPN is in use.
But can you have two Different DNS servers in the same domain with different DNS records but same WINS ? I don't think so.