In a typical production SD-WAN deployment, we would probably have many remote sites connected via many different Internet connections to a centralized data center or a regional hub. In most regions of the world, Internet providers will always use some type of private-public address translation due to a shortage of public IPv4 space.
NAT Detection
Every SD-WAN device may unknowingly sit behind a NAT device at any moment. Cisco SD-WAN devices use the Session Traversal Utilities for NAT (STUN) protocol defined in RFC5389 to discover their public IP addresses/ports allocated by NAT.