About GRE

Generic Routing Encapsulation (GRE) is a tunneling protocol that can encapsulate a protocol (such as IP, MPLS, or Ethernet) into a virtual point-to-point tunnel over a network (such as an IP network). Packets are encapsulated at one tunnel end and de-encapsulated at the other tunnel end. The network layer protocol of the packets before encapsulation and after encapsulation can be the same or different.