When to use Gre Tunnels

[opnineopnine]

Hi all,

Please can someone tell me it's what type of circumstances, you will use GRE tunnels. 

Thanks. 

[davegibelli]

The main use for GRE is to hide the network from the user(s). It also allows a stops a user from accessing devices on the network carrying the traffic assuming the user does not have access to the device doing the tunneling.

It is like IPsec without the encryption but has one advantage over IPsec in that a GRE can carry routing protocols.

[opnineopnine]

Hello,

And tunnels with no IPsec, ? 

I ask this because I have a customer with simple gre tunnels. Pointing to different places.

Regards.

[Jon Marshall]

Depends on the underlying network.

For example a company may want to use GRE tunnels on their LAN or across an MPLS network for various reasons in which case they may well run without IPSEC because these are private networks.

If the underlying network is the internet though I would expect most companies to use IPSEC with the GRE tunnels.

Jon

[Joseph W. Doherty]

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Posting

When you have a need for a p2p L3 capable link between two hosts when a physical p2p link isn't available.  Usually there's some routing issue that causes the need.

For example, I want to logically join two site networks, both using private addressing and both with connections to the Internet.  I can create a logical p2p L3 link between them using a GRE tunnel.  (If you're worried about transmitting your data across the Internet, it can be encrypted.)

BTW, there are other kinds of tunnels that might address a routing issue, but Generic Routing Encapsulation can be used in many cases, and is often supported by the equipment.

For more information, you might want to look at: http://en.wikipedia.org/wiki/Generic_Routing_Encapsulation

[Bekzod Fakhriddinov]

when u have more than 2-3 ipsec vpns from your router so u neeed to know how to route packets p to proper vpn, so you need EIGRP/OSPF/RIP , but they will not work with ipsec ,  here GRE helps you , you need to run dynamic routing and GRE so routing will properly choose route .

its from CCNP routing course . u may have DMVPN -its remote sites connected with GRE over ipsec and routing is dynamic .