FULL PRODUCT VERSION :
java version "1.8.0_91"
Java(TM) SE Runtime Environment (build 1.8.0_91-b14)
Java HotSpot(TM) Client VM (build 25.91-b14, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]
Microsoft Windows [Version 10.0.10586]

A DESCRIPTION OF THE PROBLEM :
InetAddress.isReachable reports some non existing IP addresses as reachable. Java releases 1.8.0_73 and earlier do not exhibit this problem which had been reported in JDK-8157403, but was closed prematurely.

REGRESSION.  Last worked in version 8u73

ADDITIONAL REGRESSION INFORMATION: 
java version "1.8.0_73"
Java(TM) SE Runtime Environment (build 1.8.0_73-b02)
Java HotSpot(TM) Client VM (build 25.73-b02, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the attached program with Java of versions 1.8.0_73 and 1.8.0_91 and enter a random IP address in the IP Address text field followed by an Enter key or a click on the Ping button. The result is shown in the text area.

Examples of the IP addresses:
10.11.1.2
173.168.2.1


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Both versions of Java should show those IP addresses as "NOT an active host".
ACTUAL -
Java version 1.8.0_73 shows those IP addresses as NOT active and 1.8.0_91 as active.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.BorderLayout;
import java.awt.Cursor;
import java.awt.Dimension;
import java.io.IOException;
import java.net.InetAddress;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class TestPing extends JFrame {
    public TestPing() {
        setTitle(getClass().getSimpleName() + " " + System.getProperty("java.version"));
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        JTextArea textArea = new JTextArea();
        textArea.setEditable(false);
        JScrollPane scrollPane = new JScrollPane(textArea);
        scrollPane.setPreferredSize(new Dimension(400, 300));
        getContentPane().add(scrollPane, BorderLayout.CENTER);

        JPanel panel = new JPanel();
        getContentPane().add(panel, BorderLayout.NORTH);

        JLabel lblIpAddress = new JLabel("IP Address");
        panel.add(lblIpAddress);

        JTextField textField = new JTextField();
        panel.add(textField);
        textField.setColumns(11);

        JButton button = new JButton("Ping");
        panel.add(button);
        button.addActionListener((e) -> {
            try {
                Cursor tfCursor = textField.getCursor();
                textField.setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
                setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
                InetAddress address = InetAddress.getByName(textField.getText());
                boolean reachable = address.isReachable(5000);
                textArea.append(address + " machine is " + (reachable ? "" : "NOT ") + "an active host\n");
                textField.setCursor(tfCursor);
                setCursor(Cursor.getDefaultCursor());
            }
            catch (IOException ex) {
                textArea.append("Error: " + ex.getMessage() + "\n");
            }
        });

        textField.addActionListener((e) -> {
            button.doClick();
        });
    }

    public static void main(String[] args) {
        TestPing test = new TestPing();
        test.pack();
        test.setLocationRelativeTo(null);
        test.setVisible(true);
    }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Using Java of version 1.8.0_73.