Which of the following commands could the engineer use to query the DNS server to get mail server information?

A Linux engineer set up two local DNS servers (10.10.10.10 and 10.10.10.20) and was testing email connectivity to the local mail server using the mail command on a local machine when the following error appeared:

The local machine DNS settings are:

Which of the following commands could the engineer use to query the DNS server to get mail server information?
A . dig @example.com 10.10.10.20 a
B . dig @10.10.10.20 example.com mx
C . dig @example.com 10.10.10.20 ptr
D . dig @10.10.10.20 example.com ns

View Answer

Answer: B

Explanation:

The command dig @10.10.10.20 example.com mx will query the DNS server to get mail server information. The dig command is a tool for querying DNS servers and displaying the results.

The @ option specifies the DNS server to query, in this case 10.10.10.20. The mx option specifies the type of record to query, in this case mail exchange (MX) records, which identify the mail servers for a domain. The domain name to query is example.com. This command will show the MX records for example.com from the DNS server 10.10.10.20. This is the correct command to use to accomplish the task. The other options are incorrect because they either use the wrong syntax (@example.com 10.10.10.20 instead of @10.10.10.20 example.com), the wrong type of record (a or ptr instead of mx), or the wrong domain name (example.com ns instead of example.com mx).

Reference: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 13: Managing Network Services, page 415.