Using Hyper-V with IPsec
IPsec is a standard IP security suite controlled by the Internet Engineering Task Force (IETF). Its purpose is to provide network security at the layer of the IP packet. This is a potentially powerful way to secure communications as it maintains end-to-end encryption. It is, however, not a simple technology to implement properly. Encryption at this level can cause problems for the devices that need to deliver those packets. It can also potentially be computationally expensive. You should not be implementing IPsec without an identified requirement and a thorough plan. If you've never worked with IPsec before, there are numerous guides available to help you with the process. Microsoft publishes one such guide that is available at http://technet.microsoft.com/en-us/library/bb742429.aspx.
Apart from the potentially high computational burden of running IPsec on a lot of guests in Hyper-V, there's nothing particularly special about running it in a virtual environment....