In order to ensure that only one firewall is inspecting traffic and handling address translations on your network, your office firewall must receive a Public IP address on its WAN interface.
This functionality may require the assistance of your internet service provider (ISP).
Please note that this information is provided as a courtesy. You are responsible for ensuring that minimum technical requirements for installation and provision of the Weave service are met. Additionally, you are responsible for any additional configuration and maintenance of network equipment to meet your requirements, such as security settings, firewall deployment, or other operational requirements, including, but not limited to changing default passwords and periodic hardware, software, or firmware updates.
Identifying a private (non-public IP address) is fairly easy. If your WAN has an IP address in one of the following IP blocks, it is not a Public address, and you should contact your ISP to help "Bridge" your Modem/Gateway device, allowing a Public IP address to be assigned to your firewall/router.