Win 1903 update changed the way internal IPs get processed

by MeSo2   Last Updated August 14, 2019 15:01 PM

Is it a feature or a bug?

We use IIS (Windows 10 Pro - 1903) to host our website. All requests get proxy-ed to IIS from Apache. This illustrates our Win-VM server setup.

Internet <> ISP <> G Data Antivirus <> Firewall <> Apache (proxy) <> IIS (a internal IP)

Win-VM is running in a VirtualBox setup on an Ubuntu system with two physical NICs. Win-VM gets to use both NICs: one for internal, and the other for external connections. The NICs are set up as bridged adapters in VirtualBox. Ubuntu uses only the internal NIC and gets internet access from there.

The things that are not working:

  • From within Win-VM only can be browsed, or anything else fails with The connection has timed out. Outside connections to the server work. (What would cause this?)

  • "Internal Ubuntu Systems" can browse the IIS hosted website (w/ full domain name), but doing a form method Post fails with Secure Connection Failed. "Internal Windows Systems" does not have that problem and work as expected. External connection works normally. (What would cause this behavior?)

  • The above behavior also applies to SMTP connection attempts. Ubuntu Systems fail, Window Systems connect and sends short emails to Win-VM, but sending a longer email fails. (Not sure what is going on - still investigating)

The Win-VM setup was working flawlessly before this 1903 update, now all internal connections to the server have various problem.

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