IPsec Security over a GRE Tunnel

[chuks]

I have setup a GRE Tunnel across a service provider network using cisco routers. How can I protect this tunnel using IPsec? Does anyone have any documentation on how to achieve this?

Thank you all.

[j.beckner]

I set up a 10 site network using GRE/IPSEC tunnels with EIGRP (also used dialer watch for dial backup) for one of my clients earlier this year. It works great! The following document was helpfull. (if you don't have IPX then leave that part out):

http://www.cisco.com/en/US/tech/tk583/tk372/technologies_configuration_example09186a0080093f85.shtml

[thisisshanky]

The authentication in this example is using RSA keys rather than pre-shared keys. Other than that create a basic crypto map, isakmp policy and apply it to the tunnel interface and your wan interface

http://www.cisco.com/en/US/tech/tk583/tk372/technologies_configuration_example09186a008023ce5b.shtml