Arduino Ethernet Plug-in Module

The Arduino Ethernet Shield allows an Arduino board to connect to the Internet. It is based on the Wiznet W5100 Ethernet chip. The W5100 provides a network (IP) stack capable of both TCP and UDP operation. It supports up to four simultaneous socket connections. The Ethernet shield connects to an Arduino board using long wire-wrap headers which extend through the shield. This keeps the pin layout intact and allows another shield to be stacked on top.

Arduino uses pins 10, 11, 12, & 13 (SPI) to communicate with the Ethernet shield. These pins cannot be used for general I/O
Power-over-Ethernet enabled RJ-45 Ethernet socket (current Rev 3 product)
Supplied with or without PoE module (current Rev 3 product)
Reset button on the shield resets both the W5100 and the Arduino board
Seven status LEDs
SD card slot (MicroSD on current Rev 3 product)