Interest in cloud computing is growing rapidly to changes in the network environment. Currently, one of the largest open source cloud computing platform is OpenStack. OpenStack controls the resources of compute, storage, and networking. And, virtual networking control is called Neutron. OpenStack uses VPNaaS (VPN-as-a-Service) as a extension service for site to site connections. In this paper, we describe the architecture and data model of VPNaaS. In addition, we describe how to set up VPNaaS service. And, connection procedure using VPNaaS is explained.