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New Member

GRE TUNNEL

Can anyone tell me what a GRE tunnel is and why I would need one ?

cheers

Carl

5 REPLIES
New Member

Re: GRE TUNNEL

A GRE tunnel will essentially encapsulate traffic into another packet with the IP of the source interface and destination interface (the tunnel ends).... thereby making the packet look basically liek the routers are talking to one another. This allows you to pass traffic that may otherwise not operate properly.

For example.

We have a VPN tunnel between 2 pixes. We us eigrp and IPX in our environment. IPSec does not encrypt IPX nor will the pix route the multicast EIGRP router updates. I built a gre tunnel to pass all the traffic... effectively masking the traffic to look like a standard tcp packet...

Make sense?

New Member

Re: GRE TUNNEL

So say if I have the internet at home and my friend has it too, could I create a tunnel between us ? is this not like VPN ?

New Member

Re: GRE TUNNEL

The only way it is like a VPN is that the endpoints appear to be the routers... not the pc's... the traffic is NOT encrypted !!!

So if you don't want someone to be able to capture the data... don't do it that way.

Hall of Fame Super Silver

Re: GRE TUNNEL

I would say that there are similarities between VPN and GRE. They are both based on the concept of tunneling. They both configure a relationship with a remote peer who terminates the tunnel established on the local router. They both take a packet as payload and encapsulate it with new headers.

Those are some of the similarities. The big difference is that VPN is based on IPSec and protects the traffic being transitted while GRE transmits without protecting its payload.

HTH

Rick

Bronze

Re: GRE TUNNEL

GRE is a tunneling protocol that was originally developed by Cisco, as Marty said at first reply it can be used to transport some traffic that they can't transport over some network for example multicast traffic,IPv6,IPX,AppleTalk and ...

especialy when you're going to transport those traffic over internet (TCP/IP) or when you can't transport data explicitly.

it's an unencrypted tunneling protocol and so simple to implement, in fact when you Interested in to transport ip traffic via GRE, each ip packet becomes the payload of the new ip tunnel packet.

http://www.faqs.org/rfcs/rfc2784.html

some other tunneling protocol using GRE, for example PPTP :

http://support.microsoft.com/?kbid=241251

Regards,

Mehrdad Arshad Rad

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