What NAT configuration does cPanel support?
cPanel only supports 1:1 NAT configurations. This means that there can only be a single public IP paired with a single private IP and vice versa.
cPanel also requires a working NAT loopback (hairpin NAT). This means that the server needs to be able to reach its external NAT IPs.
This is noted in our documentation:
If you use a NAT environment, your server must reside in a 1:1 NAT configuration to
install cPanel & WHM.
A 1:1 NAT and NAT loopback configuration if you server resides in a NAT-configured network.