There are two technologies today that many networks use, one of them solves traditional Layer 2 VPN challenges and another is used as a data plane in many datacenters.
EVPN VXLAN is the two technologies that come together and solves not even only Layer 2 challenges, such as loop, active-active multihoming, and fast convergence, which are hard problems to solve in Layer 2, but also come with a data plane technology that is another hard choice for the datacenters.
In the data centers, people usually don’t want to deploy MPLS and thus EVPN MPLS is not a perfect match for the data center Layer 2 control plane and data plane solutions.
EVPN is a common control plane for many services
Although EVPN is introduced as a data center interconnect technology solution, today it is used for many different purposes, and services. VPWS, Service Chaining, Internet Exchange Point deployments, Overlay IP VPNs, and many more.
When it was first introduced, it was planned for the Layer 2 VPN service.
Traditionally, VPLS has been used by many large Enterprises, Datacenter and Service Provider networks for connecting multiple sites and extending subnets.
So, when we talk about the standard-based any-to-any type of Layer 2 VPN, VPLS was the only choice.
VPLS is an IETF terminology, for the readers who use MEF – Metro Ethernet Forum terminology, it is E-LAN – Ethernet LAN Service.
With VPLS, Active-Active flow-based load balancing was one of the main concerns.
There was no ARP suppression, thus broadcast traffic handling was consuming a lot of network resources.
VPLS is a data plane learning technology, meaning MAC addresses in the network is learned by flooding.
Layer 2 frame is flooded everywhere, receiving device opens the frame, and when the MAC is known, it is mapped to the incoming interface.
EVPN is on the other side, and is a control plane learning mechanism.
MAC addresses are advertised over BGP. which is the most scalable routing mechanism.
Thus, with EVPN, we can do MAC routing.
VXLAN is a common data plane for EVPN and some other control planes as well
VXLAN is an industry-standard technology, Virtual Extensible Local Area Network, was defined for the Overlay Virtualized Layer 2 Networks over Layer 3 network was defined in RFC 7348 and today it is used together with most commonly with EVPN – Ethernet VPN.
In IETF, there are other data plane mechanisms that provide overlay services, one of them is GENEVE.
But VXLAN, is by far the most commonly deployed and known technology.
Cisco’s SDA solution for example uses VXLAN as a data plane s well.
But, VXLAN itself doesn’t come with the by default any control plane technology.
In Cisco’s SDA, the control plane that is used in conjunction with the VXLAN is LISP – Locator, and Identity Separation Protocol.
VXLan is used not just only with EVPN, it is used with LISP as well, and we can see it is used with the other control planes in the future more and more.
