What address should be used to create the customer gateway resource?

Explanations:

The private IP address of the customer gateway device cannot be used because AWS requires a public IP address for establishing a VPN connection.

The MAC address is not used for establishing a VPN connection in AWS. The MAC address operates at the data link layer, which is not relevant for IP-based VPN connections.

The public IP address of the customer gateway device is required, but since there is a NAT gateway in front of the device, the IP address seen by AWS would be that of the NAT device.

The public IP address of the NAT device should be used because the customer gateway is behind a NAT device, and AWS will only be able to see the NAT device’s public IP.