I would like to implement VPN between two sites. One site is running with Pix 520 and the second site is running with Cisco 3640 (IOS 12.0(7)).IPsec is configured on PIX with a per shared key mechanishm. What need to be done to implement site to site VPN between a router and a Pix. We have software Feature packs for Routers. Where can I use these efficiently in the process of configuration of site to site VPN. I am not sure what for these Software feature packs.