This is a test lab setup. In the final live configuration I will be using a dedicated server to host the Hyper-V 2012 R2 Server.
My lab equipment does not give me the luxury of dedicated hardware so for this lab test I have a virtual machine running under an ESXi 5.5 and in this I have installed Windows 2012 Hyper-v R2. From a Windows 8 PC I have installed a VM in the Hyper-V server and installed Windows2012 server (using Hyper-V Manager). I have created a virtual switch (external) and connected the Windows 2012 server to it.
The host Hyper-V server can ping the router to the Internet but the VM within the Hyper-V can only ping the Hyper V server and itself. It cannot see anything that is outside the Hyper-V server even though it's on the same subnet.
Hyper-V Server (Server1): 192.168.2.20
Windows 2012 server (Server2): 192.168.2.30
Gateway (broadband router): 192.168.2.1
For example. Server2 can ping Server1 but it can't ping the gateway.