In the above example this might be the 1921683345

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the customer’s premises before it was migrated into the cloud. In the above example, this might be the address for a particular server that the customer wants to move to the cloud. Provider Address (PA) This is the IP address assigned by the cloud provider to the server once the server has been migrated to the provider’s data center. In the above example, this might be, or some other address in the address space. The CA for each virtual machine is mapped to the PA for the underlying physical host on which the virtual machine is running. Virtual machines communicate over the network by sending and receiving packets in the CA space. The virtual machine’s packets are then encapsulated into new packets that have a PA as source and destination address so they can be routed over the hoster’s physical network. The standards-based Network Virtualization Generic Routing Encapsulation (NVGRE) protocol is used by Hyper-V Network Virtualization, in Windows Server 2012, to encapsulate the virtual machine’s packet inside a new packet. The header of this new packet has the appropriate source and destination PA, in addition to the virtual subnet ID, which is stored in the Key field of the GRE header. The virtual subnet ID in the GRE header allows hosts to identify the customer virtual machine for any given packet even though the PAs and the CAs on the packets may overlap. In other words, Hyper-V Network Virtualization keeps track of CA-to-PA mappings to enable hosts to differentiate packets for virtual machines of different customers. All virtual machines on the same host can therefore share a single PA, which helps increase network scalability because you only need as few as a single IP address per host, which lowers the burden on switches in the hoster’s network. The result is that Hyper-V Network Virtualization allows the hoster to run multiple customer virtual networks on top of a single underlying physical network in much the same way as server virtualization lets you run multiple virtual servers on a single physical server. Network virtualization isolates each virtual network from every other virtual network so that each virtual network has the illusion that it is a completely separate network. Multiple customers can even use the exact same addressing scheme for their virtual networks; customer networks will be fully isolated from one another and will function as if each network is the only one present with that particular addressing scheme. Hyper-V Network Virtualization also makes it easier for large enterprise to move server workloads between multiple data centers where overlapping addressing schemes exist between these data centers. Hyper-V Network Virtualization thus provides increased virtual machine mobility across data centers, hosting provider clouds, and Windows Azure.
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Hyper-V Network Virtualization enhancements CHAPTER 5 115 Hyper-V Network Virtualization enhancements in Windows Server 2012 R2 Although Windows Server 2012 provided the base functionality for implementing network
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