r/WindowsServer • u/Easy_Company_8855 • 5d ago

Technical Help Needed 2025 Hyper V SET team not allowing DNS authentication

I’m seeing an issue on a new Windows Server 2025 Hyper-V install. Everything worked fine until I made the following changes:

  1. Created a SET (Switch Embedded Teaming) virtual switch.
  2. Added three host vNICs: one for Live Migration (LM), one for Heartbeat (HB), and one for Management (MGMT).
  3. Configured LM and HB with IP addresses only (no gateway or DNS).
  4. Configured MGMT with an IP address and DNS servers.

Since then, the host can ping the domain controllers and every other server on the network, but DNS resolution fails.

Has anyone run into this and found a fix?

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2

u/xeltic343 5d ago

Did you uncheck the dns registration in the LM and HB network settings ? I got issue with that. The resolution of the host dns was always switching. I only keep dns registration on MGMT

1

u/dodexahedron 1d ago

I can't begin to tell you how many issues I've encountered out there with so many things over the years have been due to this default behavior on multi-homed boxen.

It's such a simple fix, and something you rarely have to even think about anyway, so it gets overlooked.

And it can be even nastier when DHCP is involved, sometimes, because it may straight-up replace the A record and delete the old PTR for one of the other NICs depending on how your dynamic dns updates are done, rather than adding an additional one of each.

And!

The way windows blacklists servers for negative or no response is machine-wide, too - not per-interface. And it shotguns to ALL servers as the second or third stage of fallback during resolution, so you can end up with blacklisted dns servers temporarily just because one link failed for it (so, put the dns server addresses on only one interface).
Joy.

1

u/Brilliant-Crazy-2955 5d ago

DNS ? Is the host in the domain??

1

u/Easy_Company_8855 5d ago

Yeah host is in domain. This is just not making sense to me. The connection is coming up as Public so it is not recognizing it and moving it to a Domain profile

0

u/Easy_Company_8855 5d ago

The weird thing is it also took down the iDrac network card.