A Site-to-site VPN allows users to collaborate effectively between two or more geographically different offices. As a result, this allows the sharing of files and printers securely and can also serve as a disaster recovery solution.
Make sure you are in Expert Mode for these instructions.
1. Login to Zyxel Firewall and navigate to Configuration > VPN > IPSec VPN > VPN Gateway > Add
Make sure to enter the information as displayed above. I hope this helps.