MAC Address on altera de2 board

Hope this can help you (it is a portion of the attached zip file):

/*
* get_board_mac_addr
*
* Read the MAC address in a board specific way
*
*/
error_t get_board_mac_addr(unsigned char mac_addr)
{
  error_t error = 0;
  alt_u32 signature;
  alt_u32 mac_addr_ptr = EXT_FLASH_BASE + ETHERNET_OPTION_BITS;
  
/* This last_flash_sector region of flash is examined to see if 
 * valid network settings are present, indicated by a signature of 0x00005afe at 
 * the first address of the last flash sector.  This hex value is chosen as the 
 * signature since it looks like the english word "SAFE", meaning that it is 
 * safe to use these network address values.  
*/
  /* Get the flash sector with the MAC address. */
  signature = IORD_32DIRECT(mac_addr_ptr, 0);
    
  if (signature != 0x00005afe)
  {
    error = generate_and_store_mac_addr();
  }
  
  if (!error)
  {
    mac_addr = IORD_8DIRECT(mac_addr_ptr, 4);
    mac_addr = IORD_8DIRECT(mac_addr_ptr, 5);
    mac_addr = IORD_8DIRECT(mac_addr_ptr, 6);
    mac_addr = IORD_8DIRECT(mac_addr_ptr, 7);
    mac_addr = IORD_8DIRECT(mac_addr_ptr, 8);
    mac_addr = IORD_8DIRECT(mac_addr_ptr, 9);
    
    printf("Your Ethernet MAC address is %02x:%02x:%02x:%02x:%02x:%02x\n", 
            mac_addr,
            mac_addr,
            mac_addr,
            mac_addr,
            mac_addr,
            mac_addr);
  }
  return error;
}