Example for Configuring the Headquarters (Cisco Router) to Manage Branches Using Efficient VPN and Establishing IPSec Tunnels - AR100, AR120, AR150, AR160, AR200, AR1200, AR2200, AR3200, and AR3600 CLI-based Typical Configuration Examples -
IPSec over GRE Tunnel on IOS - How to Configure Two Cisco Routers to Create Site-to-Site VPN Tunnel - UniNets Blog
Site to Site IPSEC VPN Between Cisco Router and Juniper Security Gateway