OPS335 DNS Lab

Domain Name System

In this lab you will configure a Linux host to be a DNS server for the rest of the machines in your intranet. You'll use example.org as your domain with IP addresses in the range 192.168.X.1 - 192.168.X.254. The server will handle all queries for names in the example.org domain and all reverse lookups for addresses in the given range of local IP numbers. The server will pass DNS queries for other names and addresses out to the Internet (i.e. to Seneca's DNS server).

Instructions

You're going to populate your server with the following records:

Fully Qualified Domain Name
IP Address

f13.example.org
192.168.X.1

vm01.example.org
192.168.X.2

vm02.example.org
192.168.X.3

vm03.example.org
192.168.X.4

NOTE:
For those of you using Fedora 13 installed on one removable HD and used as a host for one or more guest VMs, X will default to 122. You need at least two machines to do this lab (one host and one guest). The first will be set up as your gateway/firewall and DNS server. The others will be client hosts inside the intranet.

Here's what your network will look like:

Perform these steps on your gateway/firewall/DNS machine

• Start up your Fedora 13 PC, login as joker, open a terminal window and "su -" to root. This PC will be f13. It will be your gateway/firewall as well as the domain name server for your intranet.
• Ensure you are connected to the Internet. Use firefox to authenticate yourself so you can surf the web outside of the Seneca domain.
• Use yum to update your system if necessary.

yum update

• Use yum to install the DNS server.

yum install bind

• Also start your ssh server.

service sshd start

• Set your hostname to f13.

hostname f13

• Set your domainname to example.org.

domainname example.org

Edit /etc/named.conf

• Edit the file /etc/named.conf and enter the following: But use your own X value where applicable. If no file exists, create one. If one is already there, delete it and make a new one.

 options {
 	directory "/var/lib/named";
	auth-nxdomain no;
	forwarders { 142.204.1.2; 142.204.43.43;};
 };

 zone "localhost" {
 	type master;
 	file "localhost.zone";
 };

 zone "X.168.192.in-addr.arpa" {
 	type master;
 	file "mydb-for-192-168-X";
 };

 zone "example.org" {
 	type master;
 	file "mydb-for-example-dot-org";
 };

• Make a new directory called 'named', like this

mkdir /var/lib/named

• Now edit /var/lib/named/localhost.zone and enter the following:

 $TTL	604800
 @	IN	SOA	localhost.	root.localhost. ( 
 			1	; Serial
 			604800	; Refresh
 			86400	; Retry
 			2419200	; Expire
 			604800 ); Negative Cache TTL
 ; 
 @	IN	NS	localhost.
 @	IN	A	127.0.0.1

• Now edit /var/lib/named/mydb-for-example-dot-org and enter the following: But use your own X value where applicable.

 $TTL	604800
 @	IN	SOA	localhost.	root.localhost. (
 			1	; Serial
 			604800	; Refresh
 			86400	; Retry
 			2419200	; Expire
 			604800 ); Negative Cache TTL
 ; 
 @	IN	NS	localhost.
 f13	IN	A	192.168.X.1
 vm01	IN	A	192.168.X.2
 vm02	IN	A	192.168.X.3
 vm03	IN	A	192.168.X.4

• Next, edit /var/lib/named/mydb-for-192-168-X and enter the following:

 $TTL	604800
 @	IN	SOA	localhost.	root.localhost. ( 
 			1	; Serial
 			604800	; Refresh
 			86400	; Retry
 			2419200	; Expire
 			604800 ); Negative Cache TTL
 ; 
 @	IN	NS	localhost.
 1	IN	PTR	f13.example.org
 2	IN	PTR	vm01.example.org
 3	IN	PTR	vm02.example.org
 4	IN	PTR	vm03.example.org 

• Now set up your resolver to point to itself. Edit /etc/resolv.conf, delete what's there and enter this data instead. Remember to use your value for X.

nameserver 192.168.X.1
domain example.org

• Start your DNS server with the command

service named start

• Check that your name server is running

ps ax | grep named

• or

service named status

• When starting or restarting your name server view the log file (/var/log/messages) to ensure it started without error.
• Try a few lookups:

 host f13.example.org
 	host vm01.example.org
 	host vm02.example.org
 	host vm03.example.org
 	host cbc.ca

• Now try a few reverse lookups:

 host 192.168.X.1
 	host 192.168.X.2
 	host 192.168.X.3
 	host 192.168.X.4

Perform these steps on your Intranet machine

Use virt-manager on Fedora 13 to install at least one VM called vm01. Feel free to install several more if you have time. Make sure the host name is set to vm01 and the domain is example.org. You may use vm01 from the previous lab if you wish.

• On this machine edit the /etc/resolv.conf file and enter the following:

 nameserver 192.168.X.1
 domain example.org

• Now try the commands

 host f13.example.org
 	host vm01.example.org
 	host vm02.example.org
 	host vm03.example.org
 	host yahoo.ca

• And the commands

 host 192.168.X.1
 	host 192.168.X.2
 	host 192.168.X.3
 	host 192.168.X.4

• Now, still on the second machine, try surfing the web with Firefox. NOTE: you should not need to authenticate yourself through SeneNet on this machine.

• Finally, on all machines in your network, experiment with the following commands. Be sure to use several different command options to learn and understand how they work.

 host
 dig
 nslookup

Completing the Lab

Answer the following questions:

1. What is your full name and nine digit Seneca ID?
2. Use iptables-save command to show the rules relating to DNS. Only show these rules.
3. Show the log messages generated when starting your DNS server.
4. What is a zone file and what is it used for?
5. Name the zone files used in this lab.
6. What is the purpose of /etc/nsswitch.conf?
7. What is the purpose of /etc/resolv.conf?
8. Under what circumstances does DNS use TCP vs UDP?
9. What is meant by the term "negative cache"?
10. Name 5 top level domains.