I have Server 2008 R2, Windows 8, Server 2012 Essentials R2 installed in a tri boot machine and Windows 8.1 recently installed in another machine. The first machine has been running Hyper-V for over a year. I first started with Server 2008 R2 and then Windows 8. Both work with no issues. Then I tried Server 2012 Essentials about 6 months later. All worked no problem. I was trying to decide which one I wanted to use. This is a personal machine.

While out of town I tried to dial in and was having a problem so I asked my wife to reboot the machine. When that happened Microsoft installed an update. After that it was all downhill, I had no internet access for the host in any of the three machines. I have been searching through forums for several weeks and all I see for answers is make shift manuevers to delete and recreate the switch or uninstall Hyper-V and reinstall. I tried it all and it did not help.

I recently purchased another box and decided to put Windows 8.1 on it and install Hyper-V and try it on that machine since I had read about the drivers possibly being a problem. Even though I tried to reinstall my drivers on the tri boot machine and that did not work. Well after installing Hyper-V and creating the external switch the host lost the internet. I tried the delete the switch trick and recreate it and it did get me the internet back on this machine but when I went into the VM there was no network connection. No entry was in the Network & Sharing period.

So I am wondering how can I get the same problem with 4 different Microsoft OS products on two different computers and how come there is no clear fix from Microsoft for this problem?

My only choice now is install VMware workstation, which I dread because of the disk conversions I will have to do. They take so long to process.

Does anyone have any real answers to this problem?

I have also experienced this.   

To avoid this in the future always have more than one physical network port.  Reserve one interface for the Hyper-V host and OMG THIS SMALL TEXT BUG IS ANNOYING when setting up the Virtual Switch on the second network interface (even if it's more and they are teamed), un-check "allow management operating system to share the network adapter"

The network subsystem is still very fragile in Windows unfortunately.  It's especially frustrating when the Hyper-V host is in Core mode where you have no access to any meaningful network settings.

Thank you for that confirmation! I was reading some other posts and saw that you could have more NIC's so I went out and bought one but unfortunately it did not fit my motherboard. I did not pay any attention as to what slot types I had left that I could use. Then I had to go out of town so I did not have time to return it and try again. I will next week when I get back in town and am anxious to try again. I will look up my board and some card types so I am ready. I may buy one for the other machine too so if it works I can fix both.