In this tutorial I am going to show you how we can configure site to site VPN on two IOS routers. In this example I have used 3750 Router in emulated environment. VPN stands for Virtual Private Network, in which you extend your corporate network across internet in secure fashion. In VPN it has different types and two main types are as follows: Site-to-Site VPN Remote Access VPN Site-to-Site is manly used to do connectivity between HQ and branches. Whereas, Remote Access is mainly used by mobile user, software is installed and proper credentials provided so that they can connect to Corporate Network from anywhere and can access anything they are authorized for. Following is diagram with related information we need to start with. So there are following steps your need to do on both routers in order to make them communicate over the Service Provider Network Securely. Step 1: IKE Phase 1 Step 2: IKE Phase key Step 3: IKE Phase 2 (transform-set) Step 4: Interested traffic (wh