20 DNS server Interview Questions and Answers

DNS servers are an important part of the internet infrastructure, providing the link between domain names and IP addresses. When applying for a position that involves working with DNS servers, you can expect to be asked questions about your knowledge and experience. In this article, we review some of the most common DNS server interview questions and provide tips on how to answer them.

DNS server Interview Questions and Answers

Here are 20 commonly asked DNS server interview questions and answers to prepare you for your interview:

1. What is a DNS server?

A DNS server is a server that stores DNS records and is responsible for resolving DNS queries.

2. Can you explain the main difference between Linux and Windows DNS servers?

The main difference between Linux and Windows DNS servers is that Windows DNS servers support Active Directory integration, while Linux DNS servers do not. This means that Windows DNS servers can be used to provide DNS services for an Active Directory domain, while Linux DNS servers cannot. Additionally, Windows DNS servers support a wider range of record types than Linux DNS servers.

3. How many types of DNS servers are there in the current market? Which one do you think is better for use with cloud-based applications?

There are four types of DNS servers in the current market: recursive, authoritative, root, and caching. I think that the recursive DNS server is the best type of server to use with cloud-based applications because it can provide the user with the IP address of the requested website, even if it is not cached on the server.

4. What’s the purpose of a Reverse Lookup Zone?

A Reverse Lookup Zone is used to resolve IP addresses to hostnames. This is the opposite of a standard DNS lookup, which resolves hostnames to IP addresses.

5. What’s the purpose of an A record?

An A record is a type of DNS record that allows a domain name to be mapped to an IP address. This is the most basic type of DNS record, and is used to point a domain name to a web server.

6. What’s your understanding of MX records?

MX records are used to specify the mail servers for a domain. The MX record tells the DNS server where to route email messages for a particular domain.

7. What’s the role of PTR records in DNS?

PTR records are used to map an IP address to a hostname. This is useful for reverse DNS lookups, which can be used to help improve the security of a network by identifying hosts that are attempting to masquerade as other hosts. PTR records can also be used to help diagnose network problems by providing a way to map an IP address back to a hostname.

8. What’s the purpose of CNAME Records?

CNAME records are used to map an alias to a real or canonical domain name. This can be useful when you want to provide a friendlier or shorter name for a website or service that is actually hosted at a different domain. For example, you could set up a CNAME record for “www” that points to your actual domain name. That way, users could access your site using either www.example.com or just example.com.

9. What’s the purpose of NS Records?

NS Records are used to indicate which DNS servers are responsible (authoritative) for a given zone.

10. What does the following command do: nslookup -type=mx yahoo.com?

The command nslookup -type=mx yahoo.com tells the DNS server to look up the mail exchange records for the domain yahoo.com. This is useful for finding out which servers handle email for a given domain.

11. What is the significance of wildcard DNS entries?

Wildcard DNS entries are used to provide a catch-all for requests that cannot be matched to a specific DNS entry. This can be useful if you want to provide a default page for requests that do not match any other entries, or if you want to redirect all requests to a single page.

12. Why would you want to set up multiple DNS servers?

There are a few reasons why you might want to set up multiple DNS servers. One reason is for redundancy, so that if one DNS server goes down, there is another one that can take its place. Another reason is for performance, since having multiple DNS servers can help distribute the load and improve response times. Finally, you might also want to set up multiple DNS servers in order to provide different levels of service, such as a free DNS server for general use and a paid DNS server with premium features for power users.

13. Is it possible to manually configure an application or service to use a specific DNS server? If yes, then how?

Yes, it is possible to configure an application or service to use a specific DNS server. This can be done by editing the application or service’s configuration file and adding in the DNS server’s IP address.

14. Can you explain what recursion is in context with DNS servers?

Recursion is the process of a DNS server querying other DNS servers on behalf of the client in order to fully resolve a hostname. This can be contrasted with iteration, which is where the DNS server simply returns the best answer it has available without querying any other DNS servers.

15. What are the pros and cons of using wildcards in a DNS zone file?

The main advantage of using wildcards in DNS zone files is that it can greatly simplify the management of DNS records. For example, if you have a large number of subdomains, you can use a wildcard to automatically create DNS records for all of them without having to manually create each individual record. The downside to using wildcards is that they can potentially create security vulnerabilities if not used correctly, as they can open up your DNS server to attack.

16. What happens when a DNS lookup fails?

When a DNS lookup fails, it means that the DNS server was unable to find the IP address associated with the domain name that was requested. This can happen for a variety of reasons, such as the domain name not existing or the DNS server being down. When this happens, the user will usually see an error message.

17. How can we prevent DNS spoofing attacks?

DNS spoofing attacks can be prevented by using DNS security extensions (DNSSEC), which add digital signatures to DNS records in order to verify their authenticity. Additionally, DNS servers can be configured to use only secure protocols such as Transport Layer Security (TLS) or Secure DNS.

18. What is the most important thing to keep in mind when setting up a new DNS server?

The most important thing to keep in mind when setting up a new DNS server is to ensure that the DNS server is properly configured and that all of the necessary records are in place. If you do not have a properly configured DNS server, then you will not be able to properly resolve domain names, and this can lead to a number of problems.

19. What are some common reasons for why DNS lookups fail?

There are a few reasons that DNS lookups might fail. One is if the DNS server is down or unreachable. Another is if the DNS server doesn’t have any record of the domain you’re trying to look up. Finally, if the DNS server is configured incorrectly, it might return the wrong IP address for a domain, which would cause the lookup to fail.

20. What security measures should be taken when configuring a DNS server?

There are a few different security measures that should be taken when configuring a DNS server. First, you should make sure that your DNS server is not publicly accessible. This means that only authorized clients should be able to access the server. Second, you should configure your DNS server to use only secure protocols such as SSL or TLS. Finally, you should consider using a DNS firewall to further protect your server from malicious activity.