For those needing a good example about VPN IPSec and GRE configuration
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I just ran into a nice and consise example on how to setup a VPN IPSec and GRE connection
http://www.freeccnaworkbook.com/blog/ccna-security/building-an-ipsec-gre-tunnel -
Laurence,
Thank you for posting the link. That is a great example of using GRE tunnels which can be pretty tricky to implement. I would only add one thing to it which is that when you setup GRE tunnels you have to make sure that any dynamic routing protocol you are running does not learn the GRE destination network via the tunnel. That will result in the tunnel dropping as soon as the new route is learned and you will see the tunnel constantly flapping (going up, down and up again repeatedly). I usually use prefix lists to prevent that, but there are many other methods too.
Thanks again,
Don Pezet
Host, ITProTV -
Can you give an example of prefix?
