I have reviewed this document as part of the security directorate's ongoing effort to review all IETF documents being processed by the IESG. These comments were written primarily for the benefit of the security area directors. Document editors and WG chairs should treat these comments just like any other last call comments. 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 security considerations section refers to several other documents describing other technologies (RFC7432], [EVPN-Overlays], [RFC7623], [RFC4761] and [RFC4762]) and continues to describe that the "DCI using GWs" method covered by this document is more secure than the other method "DCI using ASBRs".