In addition to my previous post, here's a simple explanation how the virtual switches work in host and a vm.
When you create external virtual switches, also the host starts using them. Here's the Network & Sharing Center from my host, connected to the network and Internet through Hyper-V external wired and wireless switches:The prefix vEthernet is the revealing factor here, it tells that these two are not my physical wired and wireless adapters but virtual switches instead, using the host physical adapters for connection. For the virtual machines to get connected, all network traffic also from and to host must go through the external virtual switches.
Here's how the adapter view looks like:
1 = My real wired adapter
2 = The wired external switch I am de facto using at the moment on my host. It in its turn uses the physical wired adapter (#1)
3 = My real, physical wireless adapter
4 = A network bridge connecting the host wireless adapter (#3) to an external network switch (#5). When you create an external network switch assigning it to a wireless adapter, a network bridge will always be automatically created. As the Hyper-V virtual machines can only see and use a wired Ethernet connection, or rather a Hyper-V vm always sees all network adapters as wired not understanding the concept of wireless, a bridge is needed to present an external switch assigned to host wireless adapter as a wired connection to Hyper-V
5 = The wireless external switch which as told above uses the bridge (#4) to connect to host wireless adapter (#3)
6 = An Internal switch for Windows Mobile virtual machines, used for debugging / testing mobile code from Visual Studio