Maybe you saw strange board by OrangePi with two RJ45 connectors.
This board is called OrangePi R1.The processor is Allwinner H2+ and amount of RAM is 256 MB.
The ethernet interfaces are 100Mbps and the board also contains WiFi connection. (RTL8189ETV module). The R1 has one micro OTG USB interface also used for powering.
The second ethernet chip is RTL8152B by Realtek.
OrangePi R1 contains two pin headers, 26 pins - compatible with Raspberry Pi B+ and 16 pins knows from Orange Pi Zero - peripherals like USB 2.0, IR receiver or TV OUT are connected on this 16pin header.
On the bottom side, you see microSD card slot (max. 32 GB) and 16MB SPI FLASH.
This interesting board can be used like VPN gateway, firewall, small router or traffic monitoring. Do you know another using?
The price is $13.90 and shipping $3.61 in my case.