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OPS335 Lab 3

405 bytes added, 14:46, 14 February 2020
Testing
=== How DNS resolution works ===
We will review in class how the Domain Name Service works. You should also read in your own time the [https://en.wikipedia.org/wiki/Domain_Name_System#Address_resolution_mechanism the DNS article on Wikipedia] for an overview of a DNS query - especially the Address resolution mechanism] section (including the '''Recursive''' and '''caching name server''' subsections) on '''Wikipedia for an overview of a DNS query'''. The diagram shown in the WIKI is also quite simple and easy to understand. Domain Name Service is a LARGE topic but this lab provides the basic principles and essentials for this course and DNS set-up for other courses. 
= INVESTIGATION 1: CONFIGURING THE DNS SERVER =
We will now be '''installing, configuring and running a DNS server on our host'''. In most networks, the gateway would '''not''' also be a DNS server,
but if we places placed ours on a separate virtual machine we would need that VM to always be running in order for the other VMs to retrieve updates, install software, or even communicate with each other.
== Preparation ==
=== /etc/named.conf ===
When you install Bind you'll get a default '''/etc/named.conf'''. Copy this file over to a backup location and empty the original (If you have SELinux enabled - do not delete or move it the file as that will cause SELinux not to trust it). We will be writing one from scratch with only the following contents, but use your own X XX value where applicable.
<pre>
options {
directory "/var/named/";
allow-query {127.0.0.1; 192.168.XXX.0/24;}; #forwarders { 192208.16867.48222.2222; };# This one works at home forwarders { 10.102.100.21; }; # This one works at Seneca
};
zone "localhost" {
=== Zone file ===
Now edit '''/var/named/mydb-for-yoursenecaid-ops''' and enter the following (use your own X XX value and domain where applicable).
<pre>
);
@ IN NS host.yoursenecaid.ops.
host IN A 192.168.XXX.1
</pre>
# Check that the ''named'' service is running using the '''ps ax''' command (perhaps combined with '''grep'''), and separately, the '''systemctl''' command (if necessary), or check the '''/var/log/messages''' file for troubleshooting purposes.
# Once you are certain that the ''named'' service had started and runs without errors, then set it to '''start automatically''' (i.e. enable the named service) when this virtual machine boots.
# You also need to set it self '''host(127.0.0.1)''' as the primary domain name server ('''DNS1''') for your '''host''' machine to your '''host machine's ifcfg file'''<br /># If your host's external facing interface (ens33) is on DHCP, you will need to also add PEERDNS=NO to ifcfg file to prevent DHCP server from assigning the original DNS server (i.e. 192.168.40.2 which is used as forwarder instead by the DNS server you are setting up) <br /><br />'''NOTE:''' You should know how to do that, but if you forgot the procedure, refer to [http://zenit.senecac.on.ca/wiki/index.php/OPS335_Lab_1#Making_Persistent_.28Permanent.29_Network_Setting_Changes Lab 1].<br><br>
# Now that you know the service works, '''add the resource records necessary for it to provide forward lookups of the other machines in your virtual network''' (hint: You should only need three more records) and restart the service.
'''Perform the Following Steps:'''
# Note: Since you are going to save your firewall at the end of this step, you may wish to '''stop libvirtd''' and '''restart iptables ''' now in order to avoid saving the rules the libvirtd automatically adds to your INPUT, FORWARD, and POSTROUTING chains.
# You will need to update the firewall on '''host''' to allow <u>incoming</u> connections to '''port 53 for both UDP and TCP''' (i.e. the protocol and port that DNS uses).
# After you have updated your firewall, save your iptables rules.
# <b>Once you rules are saved, restart libvirtd to ensure NAT and forwarding rules are re-added.</b>
'''NOTE:''' You could just disable the firewall '''but that is a poor workaround!''' You are expected to be able to handle configuration (such as this) at this point in this course.
{{Admon/important |Host Command Doesn't Work|Your machines do not know what domain to automatically add to the end of hostnames (or believe they are still in the seneca domain). The '''SEARCH''' (or DOMAIN) parameter in the '''ifcfg-eth0''' file is used to specify your own domain (eg. '''yoursenecaid.ops''' ).<br><br>}}
<li> Add the '''SEARCH''' (or DOMAIN) parameter for your '''ifcfg-eth0''' file as shown above for your '''host''' machine.</li>
<li> Issue the '''host ''' command for all vm names and host name to make certain that is works.</li>
<li>Also on all of the VMs, install and use a text-based browser called '''lynx''' to access the Web, and test-out to see if it works by issuing the command '''lynx''' with the URL as an argument.</li><li>Experiment with the following commands:<br>
<source>
= INVESTIGATION 3: CONFIGURING THE DNS SERVER FOR REVERSE LOOKUPS =
As it stands now, your server will only handle forward resolution (converting names into addresses), but it is also common to need sometimes necessary to convert addresses back into human readable names. In some situations an For public IP addresses only your ISP will can provide this service for you, but most organizations at least need to handle their . For private networks you can set it up for your own internal addressesorganisation. You also But even if you're setting up reverse DNS on the public internet - you need to understand what information the ISP would require.
Issue the following commands on any of your VMs (once again replacing X XX with your network octet):
<source>
host 192.168.XXX.1host 192.168.XXX.2host 192.168.XXX.3host 192.168.XXX.4</source>
Each one should have failed because there is currently nothing that will handle this reverse lookup for you. This requires another zone on your server.
Add the following entry to your '''/etc/named.conf''' (once again replacing X XX with your own octet):
<pre>
zone "XXX.168.192.in-addr.arpa." {
type master;
file "mydb-for-192.168.XXX";
};
</pre>
1D ; Negative Cache TTL
);
@ IN NS host.yoursenecaid.ops.1 IN PTR host.yoursenecaid.ops.
</pre>
<ol><li>Refer to the [http://www.zytrax.com/books/dns/ch8/ ptr.html reference documentation] for '''PTR''' records.</li>
<li>Add the extra records needed to complete this zone (again, you should only need three more).</li>
<li>Restart the service and test these records to make sure they work.</li>
'''Depending on your professor you will either be asked to submit the lab in class, or online. Follow the appropriate set of instructions below.'''
===Online Submission (Peter CallaghanAhad Mammadov's Classes only)===
Follow the instructions for lab 3 on blackboard.
===In Class Submission (Murray SaulAndrew's Classes only)sections==='''Arrange evidence (command output) for each You may choose to:* Submit screenshots of these items your work on your screenBlackboard, then ask your instructor in which case you don't need to come to the lab.* Or come to review them and sign off on the lab, show me your work, and talk to me about it. I want to hear what you's completion:''ve learned and 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 are:::<span style="color:green;font-size:1.5em;">&#x2713;</span>Comment out the hostname resolution (/etc/hosts) files for ALL vms, and use '''host''' command to query from a VM, the IPADDR for:<br><blockquote>'''host.yoursenecaid.ops''' , '''vm1.yoursenecaid.ops''' , '''vm2.yoursenecaid.ops''' , and '''vm3.yoursenecaid.ops'''</blockquote><br>
::<span style="color:green;font-size:1.5em;">&#x2713;</span>'''nslookup''' information ('''A''', '''NS''', '''MX''' records) for:<br><blockquote>'''host.yoursenecaid.ops''' , '''vm1.yoursenecaid.ops''' , '''vm2.yoursenecaid.ops''' , '''vm3.yoursenecaid.ops'''.</blockquote>
::<span style="color:green;font-size:1.5em;">&#x2713;</span>'''dig +trace''' for:<br><blockquote>'''host.yoursenecaid.ops''' , '''vm1.yoursenecaid.ops''' , '''vm2.yoursenecaid.ops''' , '''vm3.yoursenecaid.ops'''.</blockquote>
::<span style="color:green;font-size:1.5em;">&#x2713;</span>Download the labcheck3.bash checking bash shell script by issuing the command:<br><br>and run '''wget httphttps://matrixict.senecac.onsenecacollege.ca/~peterandrew.callaghan/filessmith/OPS335ops335/labcheck3.bash'''<br><br>set execute permission and run the shell script on your '''host''' 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;">&#x2713;</span>Completed Lab3 log-book notes.
#What parameter did you set in that file to tell the machine to refer to your own DNS server?
#What is the purpose of the '''/etc/resolv.conf''' file?
#What is meant by the term "negative cache"?
#What are type '''A''' records used for?
#What security features are available for DNS?
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