communicate and control quorum through its own consensus protocol. If the primary
controller goes down, a negotiation takes place, and a secondary controller quickly
takes over the role of primary with no state lost, and service is resumed. While this
may sound complex, one of the key tenants for Windows Server 2016 was to simplify
Network Virtualization implementation. No matter which management toolset you
use, deployment of the Network Controllers is simple, as you’ll see later in the
chapter. Microsoft’s official page on the Network Controller can be found at:
https://technet.microsoft.com/windows-server-
docs/networking/sdn/technologies/network-controller/network-controller
So far when talking about network virtualization, I have focused on the VSID, which is
isolated through the NVGRE TNI (or with VXLAN, the VNI). However, strictly
speaking, the VSID is not the isolation boundary. The true boundary of a virtual
network is the routing domain, which has a routing domain ID (RDID), the boundary
of the routing policies that control the communication and therefore the isolation
boundary. Think of the routing domain as the container that then contains virtual
subnets, which can all communicate with each other. You may see three names used,
but they all mean a virtual network:
Virtual network: The official nomenclature
Routing domain: Name used when managing with PowerShell
VM network: Name used within SCVMMFor efficiency of communications, you may still wish to define different virtual
subnets for different locations or requirements within a virtual network (even though
you don’t have to). A virtual subnet, like a physical subnet, acts as a broadcast
boundary. Later I discuss using gateways to enable communication between virtual
networks and to the Internet or physical networks.
No separate gateway technology is required for different virtual subnets within a
single virtual network to communicate. The Hyper-V Network Virtualization
component within the Hyper-V switch takes care of routing between virtual subnets
within a virtual network. The Hyper-V Network Virtualization filter that runs within
the Hyper-V virtual switch always provides a default gateway for each virtual subnet,
which is always the. 1 address and is commonly referred to as the. 1 gateway. For
example, if the virtual subnet is 10. 1. 1. 0 / 24 , the gateway address will be 10. 1. 1. 1. The
gateway routes traffic between the virtual subnets within the same virtual network, so
it’s acting as a router.
In addition to the network controller, two other major new components to SDNv 2 fit
into the category of virtual functions: the software load balancer and the gateway.
Software Load Balancer
When providing services, it’s critical that those services be scalable and highly
available. Although it’s possible to create a single web service with a public IP address