One of the worst documented area in Virtualization, most confusing, and most troubling to Virtualization newbies is networking in a Virtualized environment. Although network settings in a virtualized environment is quite simple it requires a good understanding of few concepts and terms discussed into this post.
While virtualization architectures and how the virtualization stack makes use of the network resources of the host & host teaming are different in Virtual Server and Hyper-V, the concepts are similar for Virtual Networks.
First of all, it is important to make clear that there is no direct allocation between a virtual network card to a virtual machine and a network card used for physical server used for virtualization. The way to logically connect a network card in a VM with a physical network is to create a Virtual Network in Virtual Server or Hyper-V, as the case may be, and then logically connect the network card in the Virtual machine to this new virtual network.
There are 3 types of virtual networks in Hyper-V, which are identified according to the usage of each virtual network. These 3 types of Virtual Networks are illustrated below.
Internal network: This virtual network allows communication between virtual machines. In such networks, a packet never passes a physical network card or a network cable, but traffic in this network is only done at the physical server’s memory ram.
External Network: The only type of networks that allows to establish communication between a virtual machine and a physical network (external).
Private Network: This type of virtual networks aim to communication between the physical machine (Host) and the virtual machine running on it. As in the case of Internal network, this communication is done at the server’s RAM, no physical network traffic involved. This network type is explicitly only available in Hyper-V.
Although Private network type does not exist in Virtual Server, you can still get the same functionality using the Loopback Adapter. It follows that it is also possible to categorize Virtual Networks among those that generate network traffic (External Network) and those that do not generate network traffic (Internal and Private Network).
Uniting all of the above, the procedure is:
Create a new Virtual Network in Virtual Server or Hyper-V, this can be Internal, External, or Private.
At the time of creating this new virtual network, if you created an External network you will need to associate it with a physical network card from the physical server.
In the properties of the Virtual Machine (on the management console Virtual Server or Hyper-V) logically connect the network card from the virtual machine with this newly created virtual network
Finally in the virtual machine configure the properties of network card: IP address, netmask, DNS, Default Gateway.
Important Safety Note: In Virtual Server function as a virtual network HUB, in other words, any computer connected to this virtual network can see traffic passing through this network, while in Hyper-V virtual networks operate as a switch, setting a communication “point to point” between virtual machines is possible.
I hope I have helped you to better understand virtual networks.
This article was highly inspired by Gonzalo