Changes

== OBJECTIVE & PREPARATION==In this lab, you will configure a Linux machine to be a DNS server for the rest of the machines in your Intranet. You will '''use <u>your</u> MySeneca ID (the one based on your name, not your student number) as your domain'''. The server will handle all queries for names in the '''yoursenecaid.orgops''' domain. The server will also pass DNS queries for other names and addresses out to the Internet (i.e. to Seneca's DNS server). === Online Resources=== * [https://en.wikipedia.org/wiki/Domain_Name_System#Address_resolution_mechanism Address resolution mechanism]* [https://en.wikipedia.org/wiki/Reverse_DNS_lookup Reverse DNS lookups] === Current Configuration === 

After you have completed this lab, your '''vm1host''' VM will be running a full-featured DNS server (which is how you're going to get the '''yoursenecaid.orgops''' domain without paying for it). Unfortunately, you will be the only one using your DNS server so no-one else will be able to resolve hosts under '''yoursenecaid.orgops'''

== 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.  We will <u>not</u> be setting up our server to do [https://en.wikipedia.org/wiki/Reverse_DNS_lookup Reverse DNS Lookups] but you are expected to understand the difference. In particular, you should understand that::* Your registrar (whomever you pay for your domain, even if you run your own DNS server) is responsible for '''normal (forward) DNS resolution''' of your domain.:* Your ISP (whomever you pay for your internet connection, i.e. the company that assigned a public IP to your server) is responsible for '''reverse DNS lookups''' for your IP. 

We will now be '''installing, configuring and running a DNS server on our vm1host'''. In most networks, the gateway would '''not''' also be a DNS server,but if we 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.

First, ensure that the '''host''' and '''domain namevms''' is set correctly on each are running, and that none of your four machines (have entries for the host and three or any of the VMs via in /etc/hosts): * '''host.yoursenecaid.org'''* '''vm1.yoursenecaid.org'''* '''vm2.yoursenecaid.org'''* '''vm3.yoursenecaid.org'''  You should notice that these host and domain names are settings that are <u>local< In previous courses you may have relied on the contents of /etc/u> to each machine, e.g. hosts but you will still not be able to contact '''vm1.yoursenecaid.org''' from '''vm3'''. That occurs since use them in this course so that you are currently using the '''Seneca''' and other public can see how vital a properly functioning DNS servers which know nothing about domain name: ''yoursenecaid.org'' This preparation step server is actually unnecessary for this lab's purpose (do you know why it is unnecessary?). On the other hand, by performing the above operations, it will make things appear more consistent, and may make your life a little easier.

Use yum to install the DNS server. WeInstall Bind on your 'll be using ''host'Bind''', the most popular DNS server on the planetmachine.

When you install Bind you'll get a default '''/etc/named.conf'''. Move Copy this file over to a backup location, we and empty the original (If you have SELinux enabled - do not delete or move 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.

allow-query {127.0.0.1; 192.168.XXX.0/24;}; #forwarders { 142208.20467.1222.2222; };# This one works at home forwarders { 10.102.100.21; }; # This one works at Seneca

zone "'''seneca-id'''yoursenecaid.orgops" {

file "mydb-for-yoursenecaid-orgops";

Now edit '''/var/named/mydb-for-yoursenecaid-orgops''' and enter the following (use your own X XX value and domain where applicable).

@ IN SOA vm1host.yoursenecaid.orgops. hostmaster.yoursenecaid.orgops.( 2016010301 2018042901 ; Serial

);@ IN NS vm1host.yoursenecaid.orgops.vm1 host IN A 192.168.XXX.21

# Start it the '''named''' service with the '''systemctl''' command.# Check that itthe ''named''s 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 '''(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.

Remember that you are supposed to have a working firewall on your '''vm1host''' (and every other machine), but we will focus on our vm1 '''host''' machine for now. A <u>working</u> firewall will block requests to ports that you didn't explicitly allow. This means that at this point, your DNS server, even though it's perfectly configured, is <u>'''inaccessible'''</u> to any other machine because iptables won't allow the requests to come in(the machine can communicate with itself using the rule that allows all traffic on the '''lo''' interface).

You will need to update the firewall on '''vm1''' to allow <u>incoming</u> connections in 'Perform the Following Steps:''UDP port 53''' (i.e. the protocol and port that DNS uses). After you have updated your firewall, then save your iptables rules using whatever means worked for you in the iptables labs and add it to a shell script.

# 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.

= INVESTIGATION 2: CONFIGURING THE Before proceeding, we need to set the primary DNS CLIENT =server (DNS1 ) in your '''ifcfg-eth0''' (or ''ifcfg-en0'') file for your network interface cards for your virtual machines. Also it is a good idea to install the '''bind-utils''' package on those VMs as well in order to perform queries on your host domain name server.

Now that you've setup a DNS server on vm1 - you need to configure all our VMs to use that as ''Perform the default DNS server. You should know how to do that, if you forgot - go back to [[OPS335_Lab_1 | Lab 1]] to remind yourself.following Steps:'''

#Install the '''bind-utils''' package for your virtual machines.#You can but you shouldn't set will need to configure your host VMs to use vm1 your host's IPADDR as the '''default DNS server. DNS is a critical component of ''' (DNS1) in your network setup and if it's not working right ''ifcfg- you woneth0'''t even be able to look for a solution online (or get ''ifcfg-en0'') file for your network interface card.<br>You should know how to do that, but if you forgot the procedure, refer to this [http://zenit.senecac.on.ca/wiki page) on your host/index.php/OPS335_Lab_1#Making_Persistent_.28Permanent.29_Network_Setting_Changes Lab 1]. Also your #Modify the hostname of '''each machine''' (host is configured and all three VMs) to be a DHCP client and it gets its match what the DNS server assigned automaticallysays it is (including the domain). This will be important for services we configure in later labs.

The '''Perform the Following Steps:''' <ol><li>Issue the following commands should work as expected to verify that you set-up your DNS server correctly on all of your VMsand google and your host machine:<source>host vm1.yoursenecaid.opshost vm2.yoursenecaid.opshost vm3.yoursenecaid.opshost host.yoursenecaid.opshost google.ca</source></li>

<li>Also try the following commands:<source lang="bash">host host.yoursenecaid.orgvm1host yoursenecaid.orgvm2host yoursenecaid.orgvm3host yoursenecaid.orghost google.ca

{{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 such as 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>nslookupdig</source>Use the '''dig''' command to query your DNS server for specific records (up to this point you only have NS, A, and SOA records).</li></ol> '''Record steps, commands, and your observations in INVESTIGATION 2 in your OPS335 lab log-book''' = 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 sometimes necessary to convert addresses back into human readable names. For public IP addresses only your ISP can provide this service for you. For private networks you can set it up for your own organisation. 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 XX with your network octet):

Experiment with the following commands<source>host 192. Use the '''dig''' command to query your DNS server for specific records (up to this point you only have NS and A records)168.XX.1host 192.168.XX.2host 192.168.XX.3host 192.168.XX.4</source>

Add the following entry to your '''/etc/named.conf'''Record steps, commands, and (once again replacing XX with your observations own octet): <pre>zone "XX.168.192.in INVESTIGATION 2 in your OPS335 lab log-bookaddr.arpa." { type master; file "mydb-for-192.168.XX";};</pre> And create the following zone file: <pre>$TTL 3D@ IN SOA host.yoursenecaid.ops. hostmaster.yoursenecaid.ops.( 2018042901 ; Serial 8H ; Refresh 2H ; Retry 1W ; Expire 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></ol>

== COMPLETING THE LAB ==

You have now gained experience with some common configuration settings '''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 (Ahad Mammadov's Classes only)===Follow the instructions for named, as well as common resource recordslab 3 on blackboard.

'''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.

::<span style="color:green;font-size:1.5em;">&#x2713;</span>xYou'll get the same grade regardless of how you choose to submit your work.

==EXPLORATION QUESTIONS==

#What is the purpose of the '''/etc/resolv.conf?#What is meant by the term "negative cache"''' file?#What are MX type '''A''' records used for?