IPSec VPN tunnels can also be configured using GRE (Generic Routing Encapsulation) Tunnels with IPsec encryption. One important note to keep in mind when it comes to this implementation, is that Site-to-Site VPN networks with Dynamic remote Public IP addresses can only be brought up by the remote site routers as only they are aware of the headquarter's router Public IP address. While we’ve covered Site to Site IPSec VPN Tunnel Between Cisco Routers (using static public IP addresses), we will now take a look on how to configure our headquarter Cisco router to support remote Cisco routers with dynamic IP addresses.
This article serves as an extension to our popular Cisco VPN topics covered here on Firewall.cx.
