Did some searching to make sure I was in the right forum and this was the closest I could get...
Have 3 Windows Server 2008r2 64bit w/Hyper-V servers here. 2 of them are operating perfectly. The 3rd has a strange issue...
As soon as I enable Hyper-V network sharing on the NIC, anytime anything is done via Hyper-V management (either through the in-built manager or SCVMM) connectivity is lost on that NIC. Also, even though the VMs think they have a network connection (like say an XP VM, is able to obtain an address from the DHCP server) ping to and from said VM fails.
So Installed an extra NIC in the form on a PCI gigabit card and set that card as the Hyper-V networking host leaving the motherboard NIC for management as well as file access to the host server.
Same results. Anytime anything Hyper-V related goes to access the network, all network connectivity to the server on either NIC becomes flakey.
Reloaded the server OS from scratch to see if the issue was corruption in the stack, no dice, same results.
Hardware wise, no. It's a home lab built up over time with what was available at the time via Newegg. All identical in how 2008r2 was installed and configured and was working perfectly with 2008 (non-R2) prior to this. Did upgrade to R2 and this problem started. Formatted completely and did fresh installation of R2, same problem.
Issue happened with both the on-board Marvel as well as a PCI Netgear. No, have not reported it to MS, that's why I am here. It's a home lab so don't want to waste a support incident on this, save those for issues that arise at work.