Vide: GRE tunnel

GRE (Generic Routing Encapsulation)

Primary use of GRE was to carry non-IP protocols over IP network.
GRE is stateless and offers no flow-control mechanism. As long as the tunnel destination is routable, traffic can flow through it; no reliability or sequencing is provided.
A GRE tunnel encapsulates the original IP (or non-IP) packet inside of an outer shell.
GRE adds atleast 24 bytes of overhead, including 20 bytes of IP header. Meaning, a GRE header is a minimum 4 bytes without options.
GRE allows IP multicasting and routing protocols to travel though the tunnel.
GRE is non-secure.

Here's some video about GRE tunnel.

GRE TUNNEL

Generic Routing Encapsulation GRE Tunnel Lab 1 Trailer

GRE Tunnel Basic lab in GNS3

Cisco IPsec Site_to_Site VPN over GRE tunnel and EIGRP

IPsec over a GRE tunnel

Sphene + GRE tunneling demo for CS344 at Stanford University

Site to Site IPSec GRE Tunnel via CLI Trailer

Date: 2012-01-18 23:05:24 and last modified: 2012-01-18 23:12:50