Chapter 6. Ethernet VPN
Ethernet VPN (EVPN) has solved three interesting challenges in networking. The first is providing better L2VPN connectivity in the WAN. The second is providing an agnostic control plane to handle various data-plane encapsulations for overlay networks. The third is creating a standards-based multitenant network for hosting providers.
EVPN is powerful because it combines both Layer 2 and Layer 3 advertisements into a single Border Gateway Protocol (BGP) family. People are constantly coming up with ideas on how to use EVPN to make their networks more efficient and easier to use.
The Need for EVPN
Do we really need yet another VPN? Are existing VPNs not sufficient? These are the questions that many network engineers ask when discovering and evaluating new technology. Let’s walk through each of the problem statements in more detail.
Data Center Interconnect
Traditionally L3VPN and VPLS have been used in the WAN to provide Data Center Interconnect (DCI). However, when it came to L2VPNs, Virtual Private LAN Service (VPLS) provided the core functionality, but with a lot of drawbacks:
No active-active multihoming
No control plane or ability to create routing policies
Inefficient flooding for MAC discovery and advertisements
No intersubnet forwarding
Limited MAC mobility and asymmetric traffic flows
No advanced Ethernet Services
No choice in data-plane encapsulation
Limitations aside, VPLS is still a widely used technology in the WAN because it ...