nslookup and dig for DNS in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this nslookup command?

You run the command nslookup example.com. What type of information does this command return?

Linux CLI

nslookup example.com

A It returns the mail servers (MX records) for example.com.

B It returns the IP address associated with example.com.

C It returns the DNS zone transfer data for example.com.

D It returns the HTTP headers from example.com.

💡 Hint

Think about what nslookup does by default when given a domain name.

By default, nslookup queries the DNS server for the A record, which is the IP address of the domain.

💻 Command Output

intermediate

What does this dig command output?

You run dig +short MX gmail.com. What does this command output?

Linux CLI

dig +short MX gmail.com

A It outputs the HTTP status code of gmail.com.

B It outputs the IP addresses of gmail.com in a detailed format.

C It outputs the mail exchange servers for gmail.com in a short format.

D It outputs the DNS zone transfer data for gmail.com.

💡 Hint

The +short option simplifies the output, and MX queries ask for mail servers.

The dig command with +short and MX returns only the mail servers for the domain in a concise list.

📝 Syntax

advanced

Which dig command correctly queries the TXT records for example.com?

Choose the correct dig command to query TXT records for example.com.

A dig example.com TXT

B dig -t TXT example.com

C dig example.com -t TXT

D dig -TXT example.com

💡 Hint

dig uses the syntax 'dig domain TYPE' to query specific record types.

The correct dig syntax to query a specific record type is: dig domain TYPE.

🔧 Debug

advanced

Why does this nslookup command fail?

You run nslookup -type=MX example.com but get an error. What is the cause?

A nslookup does not support querying MX records.

B The option should be '-query=MX' instead of '-type=MX'.

C The domain name is invalid.

D The correct option is '-type MX' without the equals sign.

💡 Hint

Check the correct syntax for specifying query type in nslookup.

In nslookup, the correct syntax to specify query type is '-type MX' with a space, not '-type=MX'.

🚀 Application

expert

How to automate checking DNS A records for multiple domains?

You have a list of domains in a file called domains.txt. Which bash script snippet correctly uses dig to print each domain with its A record IP address?

A while read domain; do dig +short A $domain; done < domains.txt

B for domain in $(cat domains.txt); do dig +short A $domain; done

C while read domain; do dig +short $domain A; done < domains.txt

D for domain in $(cat domains.txt); do dig +short $domain A; done

💡 Hint

Remember the correct order of arguments for dig and how to read lines from a file.

The correct dig syntax is 'dig +short A domain'. The while loop reads each domain line by line.