On Wed, 11 Oct 2023 at 09:37, Marc <Marc@xxxxxxxxxxxxxxxxx> wrote:
Having 3 different nameservers reporting different results?
An
example I have seen quite frequently is where there is an internal DNS
which resolves local (internal) server resources and forwards anything else to an external server such as 8.8.8.8. When the internal DNS fails (typically because it's been taken down for server updates) it would be useful for clients to still have access to the external DNS - even if they can't access local resources they can still access external ones, and in reality they probably already had the internal resource IPs cached anyway. So having client DNS configured as 192.168.x.x (primary) and 8.8.8.8 (secondary) makes sense.
But as you say this isn't how resolv.conf was designed (nor other DNS clients in my experience), and configuring a client that way will cause a lot of internal requests to fail even when the local DNS is operational. It's a shame that DNS clients can't have server configurations much like MX records where a random choice is made between servers of the same priority, but lower priority options can be configured too (as that would also allow load balancing of requests across multiple servers as now). I don't know of any clients that do this, though.
Obviously there are other solutions to the problem described above (eg having multiple internal servers, although my experience was in the SOHO environment where that would be excessive). If as Rafał says Windows prioritises the first DNS option then I'm
pretty sure that wasn't always the case, but it's been well over a
decade since I got out of Windows IT support! But there are certainly use cases for allowing DNS server prioritisation in this way.
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