Simplicity does not precede complexity, but follows it
Alan Jay Perlis
Before we study how to configure network virtualization in the data center, we need to acquaint ourselves with the basics of Ethernet Virtual Private Networks (EVPN). As defined before, EVPN is a solution that provides the control plane for network virtualization. In the simplest of terms, EVPN is a technology that connects L2 network segments separated by an L3 network. EVPN accomplishes this by building the L2 network as a virtual Layer 2 network overlay over the Layer 3 network. It uses BGP as its control protocol, and in the data center it uses Virtual Extensible LAN (VXLAN) for packet encapsulation.
In this chapter you should find answers to questions such as:
What is EVPN and why is it popular?
What are the control plane models for deploying EVPN?
What BGP constructs support EVPN?
How does EVPN bridging differ from traditional 802.1Q bridging?
How do I support dual-attached hosts?
EVPN is a fairly complex solution born out of the desire to find an alternative to Virtual Private LAN Service (VPLS) in the service provider network. I find that a lot of the work is not directly relevant to EVPN’s use in the data center, though vendors won’t ever stop trying to complicate a solution. I will not be discussing the pieces that I find irrelevant to the data center. Some of this is a matter of opinion, but hopefully one born out of designing network technologies ...