With the advent of large-scale cloud computing infrastructures, network extension has emerged as a major challenge in the management of modern enterprise networks. Many enterprises are considering extending or relocating their network components, in whole or in part, to remote, private and public data centers, in order to attain scalability, failure resilience, and cost savings for their network applications. In this paper, we conduct a first study on the extension of an enterprise network while preserving its performance and security requirements, such as layer 2/layer 3 reachability, and middle-box traversal through load balancer, intrusion detection and ACLs. We formulate this increasingly important problem, present preliminary designs, and conduct experiments to validate the feasibility of our design.