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OPS335 Lab 2b

3,625 bytes added, 13:54, 6 September 2019
Andrew's sections
==ADDITIONAL IPTABLES TROUBLESHOOTING==[[Category:OPS335]][[Category:OPS335 Labs]]
===Purpose=OBJECTIVE & PREPARATION ==In Lab 2a, we set the firewall rules for your '''host''' machine. In this lab, we will '''create firewall rules for our virtual machines''' within our virtual private network. This lab will also apply '''"best practices"''' and '''"troubleshooting techniques"''' using iptables.
This lab will provide more hands-on experience with troubleshooting iptables issues.=== Online Resources===
===IPTABLES and Routing Troubleshooting Resources===
 
 
Some articles that you can use as a reference if you are still experiencing problems with iptables:
* [http://zenit.senecac.on.ca/wiki/index.php/OPS335_Lab_1#Linux_Network_Connection_Configuration_Troubleshooting Test Network Connectivity] (From Lab1)
* [http://www.microhowto.info/troubleshooting/troubleshooting_iptables.html Troubleshooting iptables]
* [https://community.rackspace.com/products/f/25/t/248 Basic IPTABLES Troubleshooting]
 ==INVESTIGATION 1: CUSTOM IPTABLES RULES ON A VM== We will now '''set iptables rules for your vm1 machine'''. '''Perform the following Steps:''' # Start your '''host''' machine, and launch your '''vm1''' machine.# Login to your '''root account''' on your '''vm1''' machine.# Issue a command (like you did in lab2a) to copy your default iptables rules to the file pathname:<br>'''/etc/sysconfig/iptables.original'''# Issue an ''iptables command'' to set the policy to disable '''all forwarding traffic''', and remove the rule that is rejecting it.# Next, set the default policy to drop '''all inbound traffic''', and remove the rule that is rejecting traffic.# Issue an iptables command to list rules for verification.<br /><br />The remaining tasks will relate to that same '''inbound''' traffic chain:<br /><br /># Issue an ''iptables command'' to delete the default ssh rule.# Issue an ''iptables command'' to add a rule that allows ssh traffic (i.e. tcp packets with destination port 22) that originates from any machine within your virtual network.# Issue an ''iptables command'' to delete the default icmp rule.# 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.# Save your rules in the location that iptables will automatically read from when it starts.# Reboot your machine and check that the new rules are being applied. If they are not, resolve this issue before moving on.# Now copy the file 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. '''Record your observations in this section on your OPS335 lab log-book''' ==INVESTIGATION 2: IPTABLES TROUBLESHOOTING CHECKLIST==
By now, you have probably discovered that a simple mistake in your iptables rules can have very serious and unexpected consequences for not only your services, but the network connectivity in general. There is a general process (checklist) that you can following to help troubleshoot iptables in order to fix the problem.
<tr><th>Step</th><td>'''Procedure'''</td><td>'''Explanation'''</td></tr>
<tr> <th>1</th><td>'''Test Network Connectivity'''</td><td>You can use the [http://zenit.senecac.on.ca/wiki/index.php/OPS335_Lab_1#Linux_Network_Connection_Configuration_Troubleshooting steps in lab 1] as a guide, but keep in mind the firewall may be blocking pings and DNS requests.</td></tr>
<tr> <th>2</th><td>'''Verify Service is Running &amp; listening on the correct interfaces'''</td><td>You should learn to read the output of '''netstat ss -atnp''' and '''netstat ss -aunp''' to complement the '''systemctl status''' command.</td></tr><tr> <th>3</th><td>'''Verify Network Connectivity by Deleting iptables Rules'''</td><td>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 deafult 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><tr> <th>4</th><td>'''List your iptables Rules &amp; 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 mahchine 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>Stopping the iptable service with '''systemctl stop iptables''' will also clear all iptables rules. Additionally, it will reset all policy to ACCEPT. <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.Don't forget to restart libvirtd service as well if this is being done on a kvm host</td></tr></table>
At this point, you should be able to understand any iptables rules you experience in this course, including the <u>default</u> ones in CentOS. If you see a iptables rule that you don't understand, you can <u>delete</u> it and see what happens. But if you simply delete this rule, take the time to figure out what that rule did and why you needed to delete it. It was likely there for a purpose (other than to drive you crazy).
'''Record the troubleshooting checklist in your OPS335 lab log-book'''
'''Record troubleshooting checklist for INVESTIGATION 1 in your OPS335 lab log-book''' ==INVESTIGATION 23: HANDS-ON IPTABLES TROUBLESHOOTING==
You will now get additional practice on troubleshooting iptables by downloading a running a shell script that will create iptables rules that will cause problems. You will then need to use tools and procedures (IPTABLES Troubleshooting Checklist) to determine the cause of the problem and fix that problem.
{{Admon/important |Backup your VMs!|You MUST perform a '''full backup''' of ALL of your VMs whenever you complete your '''OPS335 labs''' or when working on your '''OPS335 assignments'''Record steps, commands. You should be using the dump command, and you should use the Bash shell script that you were adviced to create in order to backup all of your VMs.}}  '''Record your observations in INVESTIGATION 2 in this section on your OPS335 lab log-book''' 
== COMPLETING THE LAB ==
[[Image:lab1_signoffIn completing this lab you have gained further practice using iptables.png|thumb|right|300px|Students Each of your machines should now be prepared with '''all required commands (system information) displayed in protected by a terminal custom firewall that we will continue to build on throughout the course. You have also gained experience troubleshooting iptables and determining what rules might need to be changed to allow desired traffic (or multiple terminalsblock undesired traffic) prior to calling the instructor for signoff. '''Depending on your professor you will either be asked to submit the lab in class, or online. Follow the appropriate set of instructions below.]]'''Arrange evidence  ===Online Submission (command outputPeter Callaghan's Classes only) ===Follow the instructions for each lab 2b on blackboard. ===Andrew's sections=== You may choose to:* Submit screenshots of these items your work on Blackboard, in which case you don't need to come to the lab.* Or come to the lab, show me your screenwork, then ask your instructor and talk to me about it. I want to review them hear what you've learned and sign off on answer any questions you have. You'll get the same grade regardless of how you choose to submit your work. Expected results of this lab's completionare:'''
::<span style="color:green;font-size:1.5em;">&#x2713;</span>List iptables rules for ALL machines.
::<span style="color:green;font-size:1.5em;">&#x2713;</span>Prove that you can ping and ssh from your host machines to all of your vms.
::<span style="color:green;font-size:1.5em;">&#x2713;</span>Completed Lab2 logDownload and run https://ict.senecacollege.ca/~andrew.smith/ops335/labcheck2b.bash::<span style="color:green;font-book notessize:1.5em;">&#x2713;</span>Be able to explain how you debug a connectivity problem caused by iptables.
==EXPLORATION QUESTIONS==
#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 booking looking at the table above, list the 4 tips for troubleshooting iptables (in order).<br><br>
#After completing this lab, how does the above-mentioned shell script work to cause problems with iptables?

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