Lab 4: Domain Name System (DNS)

Introduction

In this lab, you’ll learn to set up, configure, and secure DNS. It is a critical service for translating domain names into IP addresses, enabling users to access network resources using human-readable names. You’ll explore DNS configuration, including creating forward and reverse lookup zones, setting up A and PTR records, and implementing DNS security measures to prevent unauthorized modifications.

Resources to assist with the lab:

  1. Homework Questions
  2. Class Resources
  3. Classmates/Teammates
  4. Internet Resources
  5. Teaching Assistants

Please reach out to the TAs only after making a genuine effort to resolve the issue independently. While they are available to provide guidance and support, their role is to assist you in developing your understanding rather than providing immediate solutions. You are encouraged to approach challenges proactively, fostering problem-solving skills and critical thinking in the process.

Developing problem-solving skills and critical thinking is fundamental to your education and growth. These skills are emphasized as part of the Aims of a BYU Education, which seek to cultivate individuals of faith, intellect, and character. Problem-solving and critical thinking are essential components of sound reasoning, effective communication, and intellectual depth — qualities that prepare you to succeed in both academic and real-world challenges.

BYU’s focus on lifelong learning and service reminds us that the ability to independently approach, analyze, and resolve complex issues is just as important as mastering technical skills. These capabilities not only build competence but also instill the confidence to contribute meaningfully to the world and continue learning throughout life.

Configuration Instructions

Virtual Machines and Operating Systems

You will be working with:

  • 2 Ubuntu 20.04 Machines

Network Configuration

Since your machines do not currently have internet access, you will need to configure the network as follows:

  1. Lab-4-DNS Machine:
    • WAN (ens18 interface):
      • IP: 172.18.x.5/16
      • Gateway: 172.18.0.1
      • DNS: 172.18.0.1
    • LAN (ens19 interface):
      • IP: 192.168.x.10/16
      • No gateway required
  2. Lab-4-Internal Machine:
    • LAN (ens18 interface):
      • IP: 192.168.x.11/16
      • No gateway required
      • DNS: 192.168.x.10

The internal machine will not have internet access even after the network has been configured but it should be able to reach the LAN IP of the DNS server.

Accessing the Virtual Machines

Scoreboard Key

  • Green arrows indicate that everything is working as intended.
  • Orange exclamation marks indicate that something is partially working.
  • Red down arrows indicate that something is not working.

You can hover over each specific arrow, and a tooltip will appear with a hint on what is wrong or not working.

Credentials

  • All VMs have the same login credentials:
    • Username: blueteam
    • Password: abc123

File Creation and Content

  • If a referenced file does not exist, you must create it.
  • For any questions requiring files to contain specific content, use the Lab-4-DNS machine.

Domains

Internal Domains

Service Domain Name Record Types Resolving IP
DNS ns.friedchicken.local NS, A, PTR 192.168.X.10
Intranet intranet.friedchicken.local A, PTR 192.168.X.30
HR System hr.friedchicken.local A, PTR 192.168.X.31
Finance finance.friedchicken.local A, PTR 192.168.X.32
Development dev.friedchicken.local A, PTR 192.168.X.33
QA/Test qa.friedchicken.local A, PTR 192.168.X.34
Helpdesk helpdesk.friedchicken.local A, PTR 192.168.X.35
Inventory inventory.friedchicken.local A, PTR 192.168.X.36
Wiki wiki.friedchicken.local A, PTR 192.168.X.37

External Domains

Service Domain Name Record Types Resolving IP
DNS ns.friedchicken.com NS, PTR 172.18.X.5
Website friedchicken.com A, PTR 172.18.X.6
Website www.friedchicken.com CNAME, PTR 172.18.X.6
APIs api.friedchicken.com A, PTR 172.18.X.6
Status Page status.friedchicken.com A, PTR 172.18.X.7
E-commerce shop.friedchicken.com A, PTR 172.18.X.8
Blog blog.friedchicken.com A, PTR 172.18.X.9

For forward lookups, the A, NS or CNAME records must resolve and for a reverse lookup, the PTR record must resolve. Forward lookups resolve a domain to an IP address. A reverse lookup does the opposite and resolves an IP to a domain name.

Pass Criteria

P1: DNS Installation and Configuration

  1. Install DNS on the server by installing the bind9 package

P2: DNS Installation and Configuration

  1. Configure a forward lookup zone for all the domains with A records in the Internal Domains table
  2. Configure a reverse lookup zone for all the domains with PTR records in the Internal Domains table
    • You should be able to resolve the domain names from your Lab-4-Internal machine when the records have been created.

P3: Troubleshooting

To complete P3 P1-P2 must have a green arrow before starting.

  1. Fix the errors in the DNS config files to allow the service to restart.
  2. Restart the service.

Merit Criteria

M1: DNS Installation and Configuration

  1. Configure a forward lookup zone for all the domains in the External Domains table.
  2. Configure a reverse lookup zone for all the domains with PTR records in the External Domains table.

M2: DNS Security

To complete M2 P1-3 and M1 must have a green arrow before starting.

  1. Limit queries to any domain or IP in the Internal Domains table to 192.168.0.0/16.
  2. Limit queries to any domain or IP in the External Domains table to 172.18.0.0/16.

M3: Troubleshooting

To complete M3 P1-3 and M1-2 must have a green arrow before starting.

  1. Some of the domains are having issues resolving. Fix the issues.

Distinction Criteria

D1: DNS Installation and Configuration

  1. Resolve public domains using your Lab-4-DNS machine as the recursive resolver for internal IPs only. You should be able to look up public domains from your Lab-4-Internal machine but you should not be able to look up public domains from your 172.18.X.X address.

D2: DNS Security

  1. Disable zone transfers.

Submission

You don’t need to submit anything for this lab. All of the above criteria will be auto-graded unless stated otherwise. Once you have finished the lab you will have to do a verbal pass off with a TA.

Pass Off Questions

You will be asked two of these questions at random during your verbal pass-off.

  1. What command did you use to install the DNS server?
  2. Describe the purpose of a forward lookup zone and the types of records you would typically find in one.
  3. What is the function of a reverse lookup zone, and which DNS records are involved in reverse lookups?
  4. Explain the difference between an A record and a C record.
  5. How does the DNS service you configured translate domain names into IP addresses?
  6. What file did you use to define the forward lookup zones for the internal domains, and what were the contents of this file?
  7. How can you verify that forward lookups are working correctly?
  8. What command did you use to check the status of the bind9 service, and where did you store the output?
  9. When you encountered errors in the DNS configuration, what steps did you take to troubleshoot and resolve them?
  10. Why is it important to limit query access to the internal and external domains, and how did you configure these restrictions?
  11. Why are zone transfers a potential security risk, and how did you disable them?
  12. What does a recursive query in DNS mean, and how did you limit recursive queries to internal IP addresses?
  13. What are the differences between an NS record and an A record, and how did you configure the NS records for this lab?

Grading:

  • Pass: All Pass criteria and verbal pass-off has been completed.
  • Merit: All Pass and Merit criteria completed.
  • Distinction: All Pass, Merit, and Distinction criteria completed.

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