RV 50 with public IP address with IP pass through to firewall device


I have an RV 50 with a static IP address. There is a firewall device with VPN features connected to the port of the RV 50. I would like the public static IP address to pass completely through the RV 50 and to be the IP address of the WAN port of the firewall. Currently the RV 50 will assign to the firewall an IP address via DHCP. What are the settings on the RV 50 that I need to configure in order to make this happen. Thanks!