Have you recently had trouble with a VM at random times losing its network connection? On one of our Server 2008 R2 SP1 hosts, all other VMs would work great on this host, but one virtual machine would on a weekly basis timeout. This host had normal network connections, iSCSI connections to an Equallogic storage array so with SQL and web server VMs there was a great deal of data flow going through this hosts and VMs
A simple reboot will solve the issue, but with an unreliable virtual machine, that timeout could occur at any time. Numerous attempts at modifying NIC changes, toggling on/off TCP settings, cable swaps gave no such luck.
Finally started going down the hotfix route had came across this Microsoft article:
This article links you directly to the Microsoft Support’s site where you will be able to download the hotfix package or this also could be accomplished through Windows Update.
This update does require a reboot so plan accordingly, but this hotfix solved my issue. So anyone using Hyper-V with Server 2008 R2 or Server 2008 R2 SP1, this could be a great possible fix for network timeout issues in a Hyper-V environment!