[SOLVED] Guest VM DNS over VPN failing

[mightyteegar]

Strange issue, hoping it's something simple or silly.

HOST: Windows 7 professional 64-bit
GUEST: (tried with) Windows 10 TP build 101??, Windows 7 Ultimate, Ubuntu Server -- all configured with bridged adapters getting DHCP assignments from my router
VIRTUALBOX VERSION: 4.3.22 EDIT: updated tonight to 4.3.28, did not fix the problem

I have a Windows 2012 server running in Google Cloud. I have a permanent P2P IPSEC VPN configured from my router to my Google Cloud enviro. The 2012 server is configured as a domain controller (this is just for testing, please no comments about how this is not recommended) and so is running as a DNS server.

My problem is I cannot get DNS using this 2012 server to work with any Virtualbox guest. When I configure the 2012 server as the sole DNS server for the VM clients, DNS just doesn't work -- no resolution at all. I can ping the 2012 server from my guests, I can RDP to it, I can HTTP to it, I can basically do everything except DNS to that server.

When I set my host to use the 2012 server as the sole DNS server, it works fine. If I tell my guests to use Google public DNS 8.8.8.8 or Level 2's 4.2.2.2, that also works fine. I'm at a loss -- any ideas?

[mightyteegar]

Problem was a firewall rule issue on the Google Cloud side. Set an allow-all rule from my local network over the VPN and this fixed the issue.