How to build a configuration of Firewall (Brocade 5600 vRouter) that uses only one global IP?

Since the Internet gateway is redundant with VRRP, you need to assign three IP addresses.

If you use only one global IP, the following settings are required.
1.  Build the logical network with private IP address
2. Connect the Internet gateway to the logical network created in 1
3. Connect the firewall or VM to the logical network created in 1, and configure NAT so that the connection to /32 global IP can be translated.
4. Set up the Internet gateway; a static route with /32 global IP as the destination, the firewall or VM created in 3 and VM as the next hop

Service Descriptions - Internet Connectivity - Description of Functions

* More specific setting methods are outside our support range.