DHCP Address Printer

This sketch uses the DHCP extensions to the Ethernet library to get an IP address via DHCP and print the address obtained using an Arduino Ethernet shield.

DHCP is used to assign an IP address when Ethernet.begin(mac) is called. Using DHCP significantly increases the size of a sketch. Using the localIP() function, the assigned IP address is sent out via the serial monitor.

Hardware Required


The Ethernet shield allows you to connect a WizNet Ethernet controller to the Arduino or Genuino boards via the SPI bus. It uses pins 10, 11, 12, and 13 for the SPI connection to the WizNet. Later models of the Ethernet shield also have an SD Card on board. Digital pin 4 is used to control the slave select pin on the SD card.

The shield should be connected to a network with an ethernet cable. You will need to change the network settings in the program to correspond to your network.

image developed using Fritzing. For more circuit examples, see the Fritzing project page

In the above image, the Arduino or Genuino board would be stacked below the Ethernet shield.


  DHCP-based IP printer

  This sketch uses the DHCP extensions to the Ethernet library
  to get an IP address via DHCP and print the address obtained.
  using an Arduino Wiznet Ethernet shield.

   Ethernet shield attached to pins 10, 11, 12, 13

  created 12 April 2011
  modified 9 Apr 2012
  by Tom Igoe
  modified 02 Sept 2015
  by Arturo Guadalupi


#include <SPI.h>
#include <Ethernet.h>

// Enter a MAC address for your controller below.
// Newer Ethernet shields have a MAC address printed on a sticker on the shield
byte mac[] = {
  0x00, 0xAA, 0xBB, 0xCC, 0xDE, 0x02

// Initialize the Ethernet client library
// with the IP address and port of the server
// that you want to connect to (port 80 is default for HTTP):
EthernetClient client;

void setup() {
  // Open serial communications and wait for port to open:
  // this check is only needed on the Leonardo:
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only

  // start the Ethernet connection:
  if (Ethernet.begin(mac) == 0) {
    Serial.println("Failed to configure Ethernet using DHCP");
    // no point in carrying on, so do nothing forevermore:
    for (;;)
  // print your local IP address:

void loop() {

  switch (Ethernet.maintain())
    case 1:
      //renewed fail
      Serial.println("Error: renewed fail");

    case 2:
      //renewed success
      Serial.println("Renewed success");

      //print your local IP address:

    case 3:
      //rebind fail
      Serial.println("Error: rebind fail");

    case 4:
      //rebind success
      Serial.println("Rebind success");

      //print your local IP address:

      //nothing happened


void printIPAddress()
  Serial.print("My IP address: ");
  for (byte thisByte = 0; thisByte < 4; thisByte++) {
    // print the value of each byte of the IP address:
    Serial.print(Ethernet.localIP()[thisByte], DEC);


See also

Last revision 2015/08/13 by SM