General Routing Encapsulation (GRE) (Internet) A method or technique of adding an IP standard header and trailer to a message that does not follow IP protocols. The encapsulated message is sent over a public network while received messages are stripped of the wrapper and processed. This permits non-standard data (from an application like Notes or AppleTalk) and totally encrypted messages to use the Internet. The technology is an important element in Virtual Private Network (VPN) offerings.