About WAN configuration and example #347

hello guy， you did a good job on DDS router. I want to test the use of dds router over 2 computer. I saw that the case in the tutorial needs to set my public ip and private ip, and I am confused about it. I checked my network settings, the private ip is fine, but the public ip is a "private IP" provided by my ISP (Internet Service Provider), the real public ip resources are very limited, and I can't get it. This is very common in my area, almost all network devices go online this way. How should I set my ip to run the demo of wan communication in the tutorial?