Implementing Data Center Overlay Protocols

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.”

Table 3-1 “Do I Know This Already?” Section-to-Question Mapping

1. In current data center networking architecture, which network layer is used to transmit VXLAN packets or other overlay packets?

1. Overlay network

2. SD-WAN

3. Underlay network

4. MPLS

2. How many available IDs can be assigned to a VXLAN at any given time?

1. 4096

2. 160,000

3. 1 million

4. 16 million

3. Which statement about VXLAN high availability is correct?

1. For an anycast IP address, vPC VTEP switches can use the same VTEP IP address.

2. For an anycast IP address, vPC VTEP switches must use the same secondary IP address on the loopback interface.

3. Distributed anycast gateways must be connected with vPC.

4. VTEP high availability will use unicast instead of multicast communications.