vPro/AMT and Direct Access issue

On my testing lab I ran into a problem as I tried to get vPro access remotely via Direct Access based on Server 2012 R2.
It turned out that there is a problem if I used the virtual network of the Direct Access Server on the same port as the built in network port.

What happend?

I couldn’t get access to the vPro interface on the Hyper-V Host where the DA Server is running as virtual machine.
Reasearching the problem I could see If I’m switching to another vNet on an other port on the same Host the vpro webinterface appears.

In best practise the Host System shouldn’t communicate during the same network port as the virtual machines anyway but with limited ressources I ignored that.
The vPro/AMT Stuff works on a shared base with the first network port on Intels Q Chipsets.
I could reproduce this with a Q77M chip and Intel 82579LM and a Q87M with I217LM as well.

Some smaller or older servers have these kind of shared remote ports as well but in most cases the remote port is independent (HPs iLO is mostly a 100Mbit port for example).