Hyper-V Remote Administration Bug
While working on a Hyper-V 2012 R2 cluster deployment, I ran into a peculiar bug. It may not necessarily be the average bug but can be frustrating if you're unaware of the root cause.
While administering a virtual switch on another server through remote Hyper-V administration, I modified the networking properties including changing the VLAN. After saving the settings, I lost connectivity to the Hyper-V virtual machine and was unable to complete the configuration. I found that since I was administering the virtual switch remotely, it lost network connectivity before applying the VLAN settings and therefore applied the default VLAN of 0. Since the management and client networks were on the VLAN, neither could connect to the virtual machine. To solve the issue, I had to use iLO console connectivity and reset the VLAN on the virtual switch.
Lesson learned: Don't remotely administer virtual switches with VLAN on Hyper-V. You may lose connectivity to your virtual machines.
Hopefully this helps someone else avoid this issue.