Configuring a site-to-site VPN using a Cisco IOS router

In this section, we will be using the following topology as a reference for our configurations:

For this exercise, we have configured the Port Address Translation (PAT) on both R1 and R2.

Let's begin setting up the site-to-site VPN on the Cisco IOS routers:

1. Using the Cisco Configuration Professional (CCP), navigate toConfigure | Security | VPN | Site-to-Site VPN. The following window will provide two options; we are going to select Create a Site to Site VPN and click on Launch the selected task:

2. The VPN wizard provides two additional methods for configuring the VPN: Quick setup (provides default configurations) and Step by step wizard. We will choose the second option and click on Next:

3. Here, you'll need to assign the interface for the incoming VPN connection, in this case it's FastEthernet0/0. Next, set the VPN peer as 100.1.1.2 and for the authentication, we have selected the Pre-shared Keys method using cisco123 as the actual secret key...