==INVESTIGATION 1: IPTABLES RULES
AS A SCRIPT==
We will now '''set iptables rules for your vm1 machine'''
. As an alternative to editing the configuration file, you can '''place iptables commands in a script''' to be executed any time the machine boots (or any other time to you need to refresh your rules). In this way, then you can '''apply your new iptables rules to your vm2 and vm3 machines''' by using the scp command and run your shell script.
'''Perform the following Steps:'''
# Issue an ''iptables command'' to allow icmp traffic from addresses in your virtual network.
# Test that your machines can still use ping and ssh to communicate with each other.
Store the commands you used to modify the iptables into a shell script called: '''firewall_restore.bash'''<br><br>'''TIP:''' for the iptables command, use the absolute pathname (i.e. use the '''which iptables''' command). <br><br># Set up a cron entry so that your rules are automatically applied every time the machine boots.# Now copy the script to your other VMs and make it apply to them when they boot as well.
# Reboot each machine and make sure this works before you move on.
<tr> <th>3</th><td>'''List your iptables Rules & Perform a "Walk-Thru"'''</td><td>For many decades, when troubleshooting programs that don't run properly, programmers will resort to reading their "source-code" line-by-line and pretend they are the computer to perform the operation. The programmer "walks-through" the code to force them to think like a computer in order to spot and fix subtle problems.<br><br>Therefore, you can follow a packet's path as you understand it should follow. Keep in mind [http://zenit.senecac.on.ca/wiki/index.php/OPS335_Lab_2#How_Firewalls_.28iptables.29_Relate_to_the_Labs_in_this_Course the diagram from the lecture last week]. What chain applies first on which machine? What's the first rule that matches the packet? What happens if no rules match the packet?<br><br>Don't forget that even if you're tracing the path of outgoing traffic - the INPUT chain on your machine still applies (for the response that comes back to your request).</td></tr>
<tr> <th>4</th><td>'''Use the log target to list unexpected traffic'''</td><td>Add a final rule to your input chain to log all traffic. Any traffic you are allowing will have already been accepted and will not reach this rule, so you will start a log of all the packets you are not allowing. Observing the logs while you attempt to use the service that is not being allowed will show you the type of traffic you need to allow.</td></tr>
<tr> <th>5</th><td>'''Verify Network Connectivity by Deleting iptables Rules'''</td><td>As a last resort, if you have no idea what's going on and need to confirm that you're still sane - clear all the iptables rules and check your configuration then. Keep in mind that the '''iptables -F''' command will delete all your rules but will not set the default policies to ACCEPT. This will tell you for sure whether your problem was (or was not) caused by iptables.<br><br>If you do this - have a ready way to restore the rules you just deleted. Restarting the iptables service is usually a good start and a '''shell script''' to add your custom rules is a reasonable next step.</td></tr></table>
'''Record the troubleshooting checklist in your OPS335 lab log-book'''
==INVESTIGATION 3: HANDS-ON IPTABLES TROUBLESHOOTING==
===Online Submission (Peter Callaghan's Classes only)===
Follow the instructions for lab 2b on
In Class Submission=== [[Image: lab1_signoff.png|thumb|right|300px|Students should be prepared with ' ''all required commands (system information) displayed in a terminal (or multiple terminals) prior to calling the instructor for signoff'''. ]] '''Arrange evidence (command output) for each of these items on your screen, then ask your instructor to review them and sign off on the lab 's completion: '''
::<span style="color:green;font-size:1.5em;">✓</span>List iptables rules for ALL machines.
::<span style="color:green;font-size:1.5em;">✓</span>Prove that you can ping and ssh from your host machines to all of your vms.
the labcheck2b.bash checking bash shell script by issuing the command:<br><br>'''wget http:// matrix. senecac.on.ca/~ peter. callaghan/ files/OPS335/labcheck2b.bash '''<br><br>set execute permission and run the shell script on your '''c7host''' machine. ::*For '''Peter's classes''', follow his Online Submission instructions in Moodle. ::*For '''Murray's classes''', run command (piping to the '''more''' command) and show output to instructor.::<span style="color:green;font-size:1.5em;">✓</span> Completed Lab2 log-book notes.
#List 3 separate techniques that you used to help troubleshoot to detect and fix iptables from running the shell script in the previous section.
<br><br>#Without looking at the table above, list tips for troubleshooting iptables. <br><br>
#After completing this lab, how does the above-mentioned shell script work to cause problems with iptables?