Posts Tagged ‘GRE’

Encrypting GRE tunnels!

Monday, September 8th, 2008

In our Last article we looked at creating GRE tunnels between networks to allow non-routable traffic to pass between remote offices.  GRE tunnels are a great solution however the traffic passing inside these tunnels is not encrypted and thus could be intercepted by unauthorized parties. In this article we are going to look at tunneling GRE inside of IPSEC. This will allow us to get the benefits of GRE and the security of IPSEC.

 

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Create a GRE tunnel between endpoints!

Monday, September 8th, 2008

Many time it is necessary to link a remote office to your main site and today we have many technologies to accomplish this task. We have IPSEC tunnels, IP-IN-IP tunnels, and GRE or Generic Routing Encapsulation Tunnels.

Each type of connectivity offers advantages and disadvantages. Some of these tunnels can even be overlaid on top of one another. For instance IPSEC can be used in a transport mode, which allows you to use the encryption with other tunnels or protocols. For this article we are going to discuss GRE tunnels. GRE is unique as tunneling technologies go in that is started out as a proprietary protocol developed by Cisco and later adopted as a standard. GRE was invented as a way of encapsulating non routable protocols in IP which is a routable protocol. In this way protocols such as multicast (this include OSPF, EIGRP), and other protocols like IPX could be tunneled across routable links.

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