Franske ITC-2480 Lab 9

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 XXX.XXX.XXX.XXX for outside DNS lookups to function.

1. 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.
2. 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. Remember to restart your interface eth0 to apply the changes.
3. 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 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.

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 "cname" 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 cname.debserv-*.test". You should get a response similar to:

Server:		127.0.0.1
Address:	127.0.0.1#53

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

1. Congrats, at this point you have a basic domain working with a MX, CNAME, and A record.

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.