Interconnect Solution for EVPN Overlay networks

This document describes how Network Virtualization Overlays (NVO) can be connected to a Wide Area Network (WAN) in order to extend the layer-2 connectivity required for some tenants. The solution analyzes the interaction between NVO networks running Ethernet Virtual Private Networks (EVPN) and other L2VPN technologies used in the WAN, such as Virtual Private LAN Services (VPLS), VPLS extensions for Provider Backbone Bridging (PBB-VPLS), EVPN or PBB-EVPN. It also describes how the existing technical specifications apply to the Interconnection and extends the EVPN procedures needed in some cases. In particular, this document describes how EVPN routes are processed on Gateways (GWs) that interconnect EVPN-Overlay and EVPN-MPLS networks, as well as the Interconnect Ethernet Segment (I-ES) to provide multi-homing, and the use of the Unknown MAC route to avoid MAC scale issues on Data Center Network Virtualization Edge (NVE) devices.