This post I want to cover IPsec, well the tunnel mode of IPsec any.  IPSec tunnel mode is the default mode. With tunnel mode, the entire original IP packet is protected by IPSec. This means IPSec wraps the original packet, encrypts it, adds a new IP header and sends it to the other side of the VPN tunnel (IPSec peer). Tunnel mode is most commonly used between gateways (Cisco routers or ASA firewalls), or at an end-station to a gateway, the gateway acting as a proxy for the hosts behind it. Tunnel mode is used to encrypt traffic between secure IPSec Gateways, for example two Cisco routers connected over the Internet via IPSec VPN.  In tunnel mode, an IPSec header is inserted between the IP header and the upper layer protocol.Next post we will cover Transport mode.  I wanted to get off of the subject of COMPOSE as it does not apply to most people in the infosec community.