[Bug]: NAT Network DNS failure with a static Linux guest on Windows 11 / 7.2.20; connectivity restored on 7.1.14 #908

Version

7.2.20r175154

Host

Windows 11 build 26200, x86-64

Guest

Linux x86-64, systemd-networkd, systemd-resolved and dnsmasq

Component

NAT Network / DNS

Observed behavior

A static-address Linux guest cannot resolve external hostnames through the NAT Network gateway on 7.2.20. Direct queries to a reachable upstream DNS server succeed. Configuring that upstream in the guest restores resolution. After downgrading to 7.1.14r170994, the connectivity test passed on a newly created guest.

The comparison is separated in time and does not establish a perfectly isolated single-variable experiment. The exact faulty code and first affected release have not been identified.

Configuration and reproduction

1. Create a NAT Network:

VBoxManage natnetwork add --netname dns-repro --network 10.0.0.0/24 --enable --dhcp on

2. Use guest address 10.0.0.100/24, gateway 10.0.0.1, and static DNS entries 10.0.0.100 and 10.0.0.1.
3. Run dnsmasq listening at 10.0.0.100, using the system resolv.conf for upstream selection.
4. Query an external hostname through 10.0.0.1 and compare with a verified reachable upstream DNS. The gateway query times out on the affected installation.
5. Compare with a newly created guest on 7.1.14.

Expected behavior

The previously working DNS path for static guests remains supported, or its migration is documented.

Workaround

Configure a verified reachable upstream DNS for the guest/local forwarder, preserving local DNS where needed. Downgrading to 7.1.14 also restored the tested connectivity.

Related report

#447 describes a similar static-guest DNS failure. Please link/merge if appropriate.

Full paired VirtualBox logs are not attached.