CCNA network engineers entry knowledge： Network virtualization
Last time we said that the content of virtualization consists of three parts, this time we will learn about network virtualization. In fact, we should not be unfamiliar with this concept. Overlays, MPLS, LISP, Virtual routers, VRFs, etc. often mentioned can all be considered as a certain form of network virtualization.
Network virtualization is to simulate multiple logical networks on a physical network. Simply put, some functions of the network layer are separated from the hardware, and a new so-called network virtualization layer is established.
In the traditional network environment, the physical host communicates with other devices through one or more network cards, and connects to the external network through its own network card. Under this architecture, it is often achieved by deploying an application on a physical device. Network isolation, this will have two problems: 1) Some applications may be idle in most cases, 2) When the number of applications increases, the scalability problem can only be solved by adding physical devices.
The physical resources are abstracted through virtualization technology, a physical network card is virtualized into multiple virtual network cards (vNIC), and different applications are isolated through virtual machines. In this way, the above problems can be solved: 1) Using the scheduling technology of the virtualization layer Hypervisor to schedule resources from idle applications to busy applications, to achieve reasonable utilization of resources; 2) Horizontally according to the resource usage of physical equipment For capacity expansion, there is no need to add new equipment unless the equipment resources are exhausted. This architecture is shown below.
The communication between the virtual machine and the virtual machine can be completed through the virtual switch. The link between the virtual network card and the virtual switch is also a virtual link. The entire host constitutes a virtual network. If the virtual machines involve three Layer network packet forwarding is completed by another role—virtual router. Generally, the entire set of virtual network modules can be independently completed and completed by a third party, such as Open vSwitch (OVS).
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