A ConnectPort X2e Ethernet/Wi-fi Gateway (both ZB/ZigBee and SE/Smart Energy variants) allow for two possible ways to connect the Gateway to the Internet: via Ethernet/wired or Wi-Fi/wireless interface. The Device Cloud derives "Device ID" from what it considers to be a product's "Primary LAN Interface". These are two important considerations when it comes to adding the Gateway to the Device Cloud.
In the case of the CP-X2e Ethernet/Wi-fi, the Primary LAN Interface is always considered to be the MAC address of the wired Ethernet client, even though the Gateway may be connecting to the Device Cloud via the Gateway's Wi-fi!
What is the MAC address of the Wi-fi interface then? Well, it has to be different from the Ethernet MAC address, or the Gateway wouldn't be able to route its network data internally. Since the Wi-fi address has to be unique, it was decided that this Wi-fi MAC address would be exactly 1 hexidecimal digit higher than the Primary LAN Interface (i.e. the Ethernet MAC address) of the Gateway.
The above characteristic is important to know when adding the Gateway to the Device Cloud or www.livesmartlee.com, since adding the Gateway is done by using the Primary LAN Interface MAC address (i.e. what is printed on the label as the Serial Number), not the Wi-fi MAC address. This is always true, even though the Wi-fi MAC address may have been the one being "Discovered".
Example: A ConnectPort X2e for Smart Energy Coordinator has Serial Number 00409D5218AE, which we now also know as the MAC address of the Primary LAN Interface. If the Gateway were connected to the internet via the Gateway's wired ethernet connection then discovered by the Device Cloud or www.livesmartlee.com, the utility would discover that same wired Ethernet MAC address of 00409D5218AE. Now, if this same ConnectPort X2e for Smart Energy Coordinator Gateway were connecting to iDigi via the Wi-fi interface, Discovery would show MAC address 00409D5218AF (i.e. one hex digit higher than the serial number/mac address on the label), but you would still add the Gateway to the Device Cloud using the Primary LAN Interface address (the one listed on the Gateway's label as Serial Number).