=====GRE=====
**G**eneric **R**outing **E**ncapsulation protocol can be used as logical point-to-point links, encapsulating most any traffic over a tunnel as unicast. The unicast feature being useful over IPSEC as IPSEC only works over unicast traffic.

====Configuration Example====
Assuming all destinations are ''**routable**'' -- creating a basic ''**GRE Tunnel**'' over the following topology:
{{:icnd1:gre-topology.png?nolink|}}

Simple Topology--
  * 3 routers / 2 subnets
  * R1 and R3 Loopback0 interfaces
  * We will create 172.16.0.0 /30 GRE Tunnel.