Franske ITC-2480 DNS Lab

Lab Procedure

Prerequisites

1. Open an SSH console to your Linux system using the PuTTY software, login with your standard user account.
2. Make sure that webmin is installed on your system.

Install BIND & Enable Caching

1. First you will need to install bind. Bind is one of the few available DNS server applications for linux. To install it, use your favorite package manager to install bind9.
2. Now we will need to enable DNS caching and forwarding on the bind server. This will allow us to use it for DNS resolving locally, as well as speed up frequent DNS requests. To do this, open up /etc/bind/named.conf.options with your favorite text editor.
3. You are now in the local options file for bind. You will need to uncomment out the following lines:

// forwarders {
//     0.0.0.0;
// };

• Note that you will need to replace 0.0.0.0 with 172.17.139.10 for outside DNS lookups to function.

1. The reason we setup a forwarder address is so that domain requests that are not on our system are passed to another DNS server instead of being searched against the root nameservers. You may want to do this in domain or enterprise environments as most large networks have internal domain names setup that only redirect inside of a local LAN. By using a forwarder, as long as the DNS server you push requests to is able to access those internal records, you will be able to access local content from internal domain names instead of needing to rely on IP addresses.
2. To apply this change, you will need to restart the Bind DNS serice. to do this run "sudo service bind9 restart". This will restart the Bind DNS service.
3. Next we will need to change our DNS server set in /etc/network/interfaces so our eth0 interfaces uses our local system for DNS lookups. To do this, open up your interfaces file with your favorite file editor, and change the dns server to 127.0.0.1.
4. The change to /etc/network/interfaces will take effect if you restart your system. To avoid doing that you'll want to edit the /etc/resolv.conf file so that it has only one nameserver line with "nameserver 127.0.0.1"
5. To test if its working, run the command "nslookup inverhills.edu". If bind is working, you should now see the following output:

Server:		127.0.0.1
Address:	127.0.0.1#53

Non-authoritative answer:
Name:	inverhills.edu
Address: 134.29.183.71

• Notice how it shows it is using 127.0.0.1 as the server. If you do not see this, then your interface file or resolv.conf file is not set to use the local machine for DNS lookups.

Create a Domain using Webmin

1. Now we are going to use webmin to create a few different type of domain records. We will go over A (Host), AAAA (IPv6 host), MX (Mail Exchange), and CNAME (Canonical Name).
2. Open up your Webmin panel and sign in. Now that we have bind9 installed, you will need to click the Refresh Modules option on the left sidebar to have Webmin recheck the system for installed packages and services.
3. Now under the Servers tab, open up BIND DNS Server. Now under Existing DNS Zones, clock Create master zone. From here we will create a new domain name for our server to host.
4. Now use the following options, where * is your System ID that was defined in Lab 5 (just the letter of your system).

Zone type: Forward (Names to Addresses)
Domain name / Network: debserv-*.test
Records file: Automatic
Master server: Leave as your hostname
Email address: root@debserv-*.test

1. Now click the create button to add our domain. As this point you should now be on the Edit Master Zone page. From here you can add and edit domain record settings.
2. To create our A record which will point your domain to a IP address, click the Address button. For the Name enter @. the @ symbol in DNS Zones defines the parent domain. Now under address, enter your VM's static IP we set back in Lab 5 and click Create. Now return back to the main BIND DNS Server page again. When there, click the Apply Configuration option in the top right corner.
3. Now we will test the A record we just created. .use nslookup to lookup the domain you just created, which should be debserv-*.test by entering "nslookup debserv-*.test"

• Remember, * is used to represent your given letter to use in lab 5. Also, if you have issues looking up the domain, make sure that nslookup is still set to use 127.0.0.1 as the Server. If not, check your /etc/resolv.conf file.

Adding additional record types

1. Now we are going to add a few more record types to our Domain. This will include a MX (Mail Exchange) and CNAME (Canonical Name) record.
2. We will start with the MX record. MX records are used by email servers to look up where to forward email for a specific domain.
3. So to create a MX record we will use Webmin again. In Webmin on the BIND DNS Server page, click the domain on the bottom named debserv-*.test and then click the Mail Server button. Under name, enter @ again, and for the address enter your VM's static IP address. Now for Priority, enter 1. The Priority entry allows people to define more than 1 MX record for a domain, and the Priority defines which one should be used before the rest.
4. Now go back to the domain zone overview page. We are now going to create a CNAME record. CNAME records are useful as they allow you to create virtual A records, but point them to a domain name instead of a host. This is most helpful in situations where you have a dynamic IP address on a system that always has a common DNS name.
5. Now on the Edit Master Zone page for your domain, click the Name Alias button. For the Name, enter "blog" and for the Real Name, enter your domain "debserv-*.test." but remember to put a period at the end of the domain as this is an absolute name. Then press create to add the record.
6. Now press the Apply Configuration option in the top right of the page again. This will apply the records you have created. Now back in putty, run "nslookup blog.debserv-*.test". You should get a response similar to:

Server:		127.0.0.1
Address:	127.0.0.1#53

blog.debserv-*.test	canonical name = debserv-*.test.
Name:	debserv-*.test
Address: 172.17.50.XXX

1. Now we are going to create a virtual web host in apache that listens for the domain blog.debserv-*.test, and then forwards you directly to your blog folder.
2. In Webmin under the servers tab, select Apache Webserver. Then on the top, click the Create virtual host button and use the following Configuration:

Handle Connections to Address: any address
Port: 80
Document Root: /var/www/blog/
Server Name: blog.debserv-*.test
Add virtual server to file: new file under virtual servers directory
Copy directives from: nowhere

1. When done, press Create Now. When you are back at the Apache Webserver page, then click Apply Changes in the top right.
2. Now in a SSH session, open up your favorite command line web browser like w3m and visit blog.debserv-*.test. Notice how you are now visiting the blog directly, instead of your modified index.html file. This is because we setup a virtual host in apache that listens for requests directly from the CNAME we created.
3. Congrats, at this point you have a basic domain working with a MX, CNAME, and A record.

Adding a AAAA record

1. Now we are going to add an AAAA (IPv6 host) record to our domain. To do this, we will first need to make sure that IPv6 networking is setup in our virtual machine.
2. In putty, using your favorite text editor, open up /etc/network/interfaces. We are going to enable IPv6 autoconfiguration to make sure that IPv6 is running on our VM. Add "iface eth0 inet6 auto" to the end if the eth0 configuration to do this. Your interface should now look similar to this:

auto eth0
iface eth0 inet static
	address 172.17.50.xxx
	netmask 255.255.255.0
	gateway 172.17.50.1
	dns-nameservers xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx
iface eth0 inet6 auto

1. Afterwords, restart the eth0 interface by using "ifdown eth0 && ifup eth0". Remember that you need to run both of these commands (hint there are two commands on this line) as root otherwise it will not work.
2. Now use ifconfig to find your IPv6 address. Remember this as we will use it in webmin to create our AAAA record.
3. Back in webmin, under servers and BIND DNS Server, select your debserv-*.test domain from the bottom and then click the IPv6 Address button. For the name, enter @ and for the address enter your IPv6 address WITHOUT the subnet prefix. It should look similar to this. 2607:f930:1c00:50:xxxx:xxxx:xxxx:xxxx
4. When done press create. Remember to press the apply configuration button in the top right to make these changes applied. Now use nslookup to lookup your domain, and notice how you now have a IPv6 and IPv4 record for your domain.
5. Congratulations, you have now setup a dual-stack DNS server for your debian server.

Adding a Delegated Domain

1. Now we are going to add another domain to the system, but this domain is a delegated domain. Luckily we can add this to BIND the same way we added our first domain.
2. So in Webmin, go to Servers, then BIND DNS Server. Then under Existing DNS Zones, Click on Create Master Zone and use the following settings:

Zone type: Forward (Names to Addresses)
Domain name / Network: *.itc2480.campus.ihitc.net
Records file: Automatic
Master server: Leave as your hostname
Email address: root@ *.itc2480.campus.ihitc.net

• NOTE: the * stands for your hostname letter, the same as you used for the other domain we created.

1. Now using webmin, create an A record for @ the same way as we did for the last domain. If you need help with this step, you can review the process we did earlier.
2. Create an MX record for the domain which directs mail for your delegated domain to your system as well.
3. Test your setup using a web browser on your local computer, can you access your webserver by going to http://*.itc2480.campus.ihitc.net (where * is your hostname letter)?

Manually editing a zone file

1. Lastly we are going to look at the domain zone file. While webmin provides a nice interface to add records, all it is doing is manually adding our records to our zone file. When you use BIND for DNS, every domain created gets its own record file which is called the zone file. In this file all subdomains and records are stored for said domain.
2. By default, the location for these records will be in /var/lib/bind, so cd into that folder and ls the contents.
3. Now, with your favorite text editor, open up the file. It should look similar to this:

$ttl 38400
debserv-A.test.	IN	SOA	VMHostname. root.debserv-A.test. (
			1395013947
			10800
			3600
			604800
			38400 )
debserv-A.test.	IN	NS	VMHostname.
debserv-A.test.	IN	A	172.17.50.XXX
debserv-A.test.	IN	MX	1 172.17.50.XXX
cname.debserv-A.test.	IN	CNAME	debserv-A.test.

1. Notice the formatting for domain records. Each record is defined by the domain or subdomain, IN, then the record type, followed by what the record is pointed to.
2. For this example, we want to change the MX priority from 1 to 10, so change the MX record settings using your text editor.
3. When you are done, restart the bind9 service to reload the changes. We will now use a new command, dig, to lookup the record to make sure the changes were applied correctly.

• Note: when restarting bind, if you have any errors restarting the service this normally means you have a typo in one of your zone files. If this is the case, go through the file again in a text editor to make sure you did not add anything extra.

1. dig is a very powerful DNS tool that allows you to lookup specific records for DNS domains, as well as many other things such as PTR, or reverse records. For our reasons though, we will use it to lookup the edited MX record. To do this, run "dig MX debserv-*.test".

• Note: If you are having issues, add @127.0.0.1 to the end of the dig command to force dig to use the local DNS server.

1. You should see the following response:

; <<>> DiG 9.8.4-rpz2+rl005.12-P1 <<>> MX debserv-*.test @127.0.0.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 59875
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;debserv-*.test.			IN	MX

;; ANSWER SECTION:
debserv-*.test.		38400	IN	MX	10 172.17.50.XXX.debserv-*.test.

;; AUTHORITY SECTION:
debserv-*.test.		38400	IN	NS	VMHostname.

;; Query time: 4 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Sun Mar 16 20:40:02 2014
;; MSG SIZE  rcvd: 78

1. Notice how the Answer Section shows the MX record is pointed to the IP of the domain, and that the priority is set to 10.
2. Congrats, you have now setup a functional DNS server.