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I think this question has been asked previously, but I can't seem to find the right answer. How do I set up split DNS on my Windows server, such that a particular FQDN should be server one of 2 types of IP addresses - if the request comes in from an endpoint based locally (LAN) then the private address is served and if the request comes from outside(Internet) then the global address (NATTed) address is served?

How do I do this configuration? Or are there other more clever solutions to circumvent this issue - currently I have configured the DNS to serve GLOBAL address (NATTed) but this is causing even the local clients to reach the destination in a roundabout fashion whereas if they were served the local address, they could reach their destination directly.

The DNS server is placed "inside".

I have looked at the following options:

Option 1: https://docs.microsoft.com/en-us/windows-server/networking/dns/deploy/split-brain-dns-deployment

This is not possible to configure because the DNS server has only a single interface, and it is not able to differentiate queries coming from outside vs. inside, because the request when it comes from outside, is "un-natted" by the firewall, so it looks like an inside request itself.

This is the same reason why I'm unable to configure - (Option2) https://docs.microsoft.com/en-us/windows-server/networking/dns/deploy/split-brain-dns-deployment - because when the traffic reaches the DNS server it looks like internal traffic itself.

So, what options do I have to configure this correctly?

Thank you!

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If you can't add a 2nd NIC (why not?), you can alternatively add a second IP address to the server NIC and use that for the DNS policy, as it requires a dedicated IP address (layer 3), not necessarily a dedicated NIC (layer 2).

One of the IP addresses you point to from the NAT router, the other you use for your LAN clients.

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  • This is working, I can't do second NIC, but I didn't know it was possible to add 2 IPs to the same NIC, thanks!
    – stealthmode
    Jul 22, 2022 at 9:04
  • Adding multiple IP addresses to a single NIC shouldn't be a problem, from the same and even from different subnets (that sometimes even makes sense). :-)
    – Zac67
    Jul 22, 2022 at 10:09

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