The Multinet ecap Stuart explained a while ago here on HECnet, I'll resend it. GRE is a IP protocol, like TCP and UDP. If you encap anything in GRE you have: IP header GRE Header (Protocol you are transporting part of GRE header represented with the 16 bit ether-type) Payload. csum In the case of DECnet the cisco encap is take the stuff you put in a etchernet packet, but skip headers and start at the protocol ID. Remember check what hapens with packets that decnet multicats on a lan. http://en.wikipedia.org/wiki/Generic_Routing_Encapsulation Let me knew if you run in to problems or need a tunnel to debug against. --Peter -----Original Message----- From: owner-hecnet at Update.UU.SE [mailto:owner-hecnet at Update.UU.SE] On Behalf Of Dave McGuire Sent: 22 June 2012 19:34 To: hecnet at Update.UU.SE Subject: Re: [HECnet] DECnet User Mode Router - Encapsulation Formats On 06/22/2012 02:31 PM, Rob Jarratt wrote: I am making a little progress on a user mode DECnet router that will run on Raspberry Pi and on Windows. There is still a long way to go, but I want to get the basic design right in terms on the network interfacing. Can someone tell me how Cisco and Multinet encapsulate DECnet packets sent over the internet? Ciscos can encapsulate DECnet within either GRE or L2TP. -Dave -- Dave McGuire, AK4HZ New Kensington, PA I hope GRE and L2TP aren't too complex. It *looks* like GRE can be transported over UDP. L2TP looks a bit more complex, but I have skimmed the Wikipedia page for all of 15 seconds so I may have missed something. Regards Rob