So I got two new servers a Dell R620 and a R720 running Hyper-V on Windows 2012 R2 all clients on them are 2012 or 2012 R2.
All NICs are Broadcom NetXtreme, 2 quad port per server, I am currently running 15.6.0.10 drivers with 7.6.15 firmware on the R720 and 16.2.0.4 drivers and 7.8.16 firmware on the R620. No guest NICs are teamed.
In the last 2 weeks I had two guest NICs in hyper-v (with a few days between) on the R620 and 1 on the R720 fail to a point where the NIC cant communicate with the network, getting a 169.x.x.x IP address. I delete the NIC in the Virtual Switch Manager, re-add it and everything is fine again. I don't allow the managing OS to share the network adapter, for the most part, I use 1 NIC per VM.
I recall this happening back with Hyper-V 2008 R2 as well, but generally at the time of a driver update or some sort of change. These Hyper-V hosts have no received any drivers, firmware or Microsoft updates anywhere around the time of these failures.
Any ideas?