Canonical URL: ; File formats: Plain Text PDF; Status: PROPOSED STANDARD; Updated by: RFC ; Authors: D. Generic Routing Encapsulation (GRE) is a tunneling protocol developed by Cisco Systems that can encapsulate a wide variety of network layer protocols inside. If the de-encapsulating router has a route for the un-encapsulated destination address going back to the encapsulating router, you will get a.

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Indicates the Strict Source Route bit.

Then, the IP protocol is responsible for forwarding the packet. The Recursion field increases by one after each encapsulation. Jun 21, Cisco’s documentation seems to demostrate that they use this exact behavior to make a keepalive work.

Generic Routing Encapsulation

Bits are reserved for future use. Indicates the Key field.

This must be set to 0. GRE 0 Protocol Type: This article needs additional citations for verification.


Email Required, but never shown. The rule says Router B needs to drop the packets rather than sending them back the direction from which they came. The offset field indicates the octet offset from the start of the Routing field to the first octet of the active Source Route Entry to be examined.

One or more could be using static routes or PBR.

False] [Frame is ignored: After receiving a certain network layer protocol such as IPX packet that needs to be encapsulated and routed, the system adds a GRE header to the packet, and then encapsulates the packet into another protocol such as IP. Rfv is nothing to say that the two routers are running a routing protocol between them, so they could have entirely different ideas of which way to send a packet.

Not set Fragment offset: Sorry, your blog cannot share posts by email. Thanks for the answer. False] [Protocols in frame: Occhiogrosso February 6, at 7: Ver 3 bits Contains the version number. Written by Stephen J. This is an entirely plausible scenario if the rule is not followed. Indicates the Ge Number Present bit.


RFC – Generic Routing Encapsulation (GRE)

It is used by the receiver to authenticate the received packet. Routing 32 bits The Routing field is optional and is present only if the Routing Present bit is 284 to 1.

Configuration Request 0x01 Identifier: Sign up or log in Sign up using Google. Globally unique address factory default Type: The tunnel source can be a physical interface or an IP address just keep in mind the tunnel source needs to be local on the router.

Retrieved from ” https: Views Read Edit View history. Indicates the Routing Present bit. Post as a guest Name.