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New Member

GRE Tunnel Establish


I want to establish a GRE Tunnel between our center office and branch office through Internet. But just center office have some internet IP address.Our branch office dialer up Internet by ISDN or ADSL. And they get dynamic IP address form ISP. So I can not set another side IP address on router config. Who can help me work out the problem?

New Member

Re: GRE Tunnel Establish

You can use dynamic crypto maps to do this with IPSec. I'm not sure if you're using GRE (like a regular router tunnel interface).

The remote end will have to establish the connection.

Something like this would work:

crypto ipsec transform-set rtpset esp-des esp-md5-hmac

crypto dynamic-map rtpmap 10

set transform-set rtpset

crypto map rtptrans 10 ipsec-isakmp dynamic rtpmap

Of course, you will need the access-list, ISAKMP statements, etc to finish the config.

Hope this helps get you going.

New Member

Re: GRE Tunnel Establish

Thank you, first.

I have finished to establish IPSec Tunnel between center and branch office. But I just use access-list to control IPsec Tunnel building. I can not do any way to eshtablish GRE Tunnel in the situation. Can you give me a example like it?