Introduction to Hyper-V Network Virtualization (HNV)

An article by Aidan Finn from Petri IT Knowledgebase

Today I'll walk you through the basics of Hyper-V Network Virtualization (HNV), including how multitenant computing works and its challenges. I'll also go into the concepts of how HNV is implemented in Windows Server 2012, Windows Server 2012 R2, and System Center.

Challenges of Multitenant Computing

Much of what Microsoft has done with Hyper-V and System Center in the 2012 and 2012 R2 generations was based on their own development and experiences in Windows Azure, as well as the feedback that was gathered from hosting companies. A key trait of a cloud is multitenancy, in which multiple customers of the cloud (known as "tenants"), rent space in the cloud and expect to be isolated from each other. Imagine Ford and General Motors both wanting to use the services of same public cloud. They must be isolated. In doing so, the cloud operator (the hosting company) must ensure that:

  • Customers cannot communicate with each other: This is not only to prevent data leakage but also to prevent deliberate (corporate espionage) or accidental attack (via infection).
  • Hosting companies cannot trust their tenants: Some customers do very dumb things, like, oh, opening TCP 1433 to the world and/or using “monkey” as their root/Administrator password. A hosting company cannot let a successful attack on a tenant compromise the hosting infrastructure and all of the other tenants along with it.

As Microsoft found out, achieving this level of isolation with traditional solutions isn’t easy. How is this done with physical networking? The answer is probably to have one or more virtual local area networks (VLANs) per tenant, with physical firewall routing/filtering to isolate the VLANs. However, this is not VLANs' intended purpose. They were meant to provide a method to subnet IP ranges on a single LAN and control over broadcast domains.

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