The adoption of server virtualization has been increasing rapidly. Server virtualization provides flexibility and agility in provisioning and placement of computing workloads. However, network connectivity has not kept pace with such innovations in the computing environment, although it still offers a rigid approach to provisioning transport services.
As a solution, network overlays abstract the details of the physical network, making it much faster to connect virtual machines (VMs) and other devices. Rather than provision paths on physical devices, overlays encapsulate traffic using protocols such as Overlay Transport Virtualization (OTV) or Virtual Extensible LAN (VXLAN) across the physical network. These newer protocols allow operators to move beyond the limitations of VLANs, which support only 4096 virtual networks, so that they can better support multitenant services.
This chapter covers the following key topics:

Virtual Extensible LAN (VXLAN) Overview: This section discusses the Layer 2 VLAN extension to provide multitenant flexibility, high segment scalability, and Layer 2 spanning tree improvement, along with a configuration example.

“Do I Know This Already?” Quiz
The “Do I Know This Already?” quiz enables you to assess whether you should read this entire chapter thoroughly or jump to the “Exam Preparation Tasks” section. If you are in doubt about your answers to these questions or your own assessment of your knowledge of the topics, read the entire chapter. Table 3-1 lists the major headings in this chapter and their corresponding “Do I Know This Already?” quiz questions. You can find the answers in Appendix A, “Answers to the ‘Do I Know This Already?’ Quizzes.”

Caution
The goal of self-assessment is to gauge your mastery of the topics in this chapter. If you do not know the answer to a question or are only partially sure of the answer, you should mark that question as wrong for purposes of the self-assessment. Giving yourself credit for an answer you correctly guess skews your self-assessment results and might provide you with a false sense of security.