In 1570RAppliances, the two SFP ports are associated with DMZ and WAN. DMZ can already be used for an internal-network, but WAN is reserved for internet-connections.
With this feature, you can use the WAN port, usually reserved for internet (external) connections, for LAN (internal) connections. Some users prefer using SFP (fiber) for internal-networks (LAN), as it is more reliable in an environment with high electrical power.
When assigned to a LAN, the WAN port can be used for any type of internal network except for a BOND network. The WAN port (like the DMZ port), can only be used for a BOND network as part of an internet (external) network.
The WAN as LAN feature is disabled by default.
For more information, see WAN as LAN.