I'm trying to establish one half of a GRE tunnel, the other being configured by my service provider. I have a Cisco PIX-506-E running Firewall version 6.3(5).
Provider Router Public IP: 8.8.8.8 My PIX Public IP: 7.7.7.7
Provider Tunnel Address: 192.168.99.1/30 My Tunnel Address: 192.168.99.2/30
Sorry, but a PIX/ASA device is not capable of being an endpoint for GRE tunneling. You'll need a router device instead.
Cisco ASA devices don't support being GRE tunnel endpoints. You need to use a Cisco router if you want a Cisco device terminating that tunnel.
Here is a guide for Setting up a GRE Tunnel on a Cisco router but as the poster above said, you need a router, not an ASA device.