Version (3 bits) GRE Version number set to 0. Reserved 0 (9 bits) Reserved bits set to 0. Set to 1 if a sequence number is present. The extended version of the GRE packet header is represented below:Ĭ (1 bit) Checksum bit. Packet header Extended GRE packet header (RFC 2890) Better throughput may be achieved by using Equal-cost multi-path routing. įor performance reasons, GRE can also be encapsulated in UDP packets. GRE packets that are encapsulated within IP directly, use IP protocol type 47 in the IPv4 header's Protocol field or the IPv6 header's Next Header field. It may be viewed as a separator between two different protocol stacks, one acting as a carrier for another. Distributed denial of service (DDoS) protected appliance to an unprotected endpoint.Įxample protocol stack OSI model layerīased on the principles of protocol layering in OSI, protocol encapsulation, not specifically GRE, breaks the layering order.Linux and BSD can establish ad-hoc IP over GRE tunnels which are interoperable with Cisco equipment.In A8/A10 interfaces to encapsulate IP data to/from Packet Control Function (PCF).In conjunction with IPsec VPNs to allow passing of routing information between connected networks.

In conjunction with PPTP to create VPNs.Generic Routing Encapsulation ( GRE) is a tunneling protocol developed by Cisco Systems that can encapsulate a wide variety of network layer protocols inside virtual point-to-point links or point-to-multipoint links over an Internet Protocol network. Cisco tunneling protocol Generic Routing Encapsulation Communication protocol

What is gre tunnel