Power DNS Slave Setup

Can I use my local network IP to setup a slave server? Or do I have to have a second public static IP address for ns2. I currently have ns1 and ns2 pointing to the same public IP.

I tried setting up the slave server with my local IP address but this did not work. I also tried my public IP address but still was unable to sync.

Environment - Hosting websites at home on my personal servers with one static IP address and two systems running Ubuntu 18 Cyberpanel.