You want to ask the specific name server 8.8.8.8 for the MX records of example.com, bypassing whatever is configured in /etc/resolv.conf. Which command does this?
LPIC-1 Exam 102-500, objective 109. Networking fundamentals medium
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How these questions are written — where each question comes from, what the verification ledger records, and what happens when one is found wrong.
The options
Not correct dig example.com MX 8.8.8.8
Wrong. Without the @ prefix, 8.8.8.8 is read as another name to look up, so dig queries your configured resolver for both example.com and the name 8.8.8.8.
Correct dig @8.8.8.8 example.com MX
Correct. The @server argument names the server to query, followed by the name and then the record type.
Not correct dig -s 8.8.8.8 -t MX example.com
Wrong. dig has no -s option for choosing a server; the server is always given as @server. (-t TYPE is a valid way to state the record type.)
Not correct getent hosts example.com MX
Wrong. getent hosts queries the NSS hosts database and only ever returns addresses. It cannot request a record type and cannot target a particular server.
Why
dig's argument order is `dig [@server] name [type]`. Both `dig @8.8.8.8 example.com MX` and `dig @8.8.8.8 -t MX example.com` work. The equivalent with host is `host -t MX example.com 8.8.8.8`, where the server is the trailing positional argument, and with nslookup it is `nslookup -type=MX example.com 8.8.8.8`.
Where this comes from
- Cited
- manual page dig(1)
Practise this
Reading one question is not practice. The trainer will draw a short set from objective 109 and space the ones you get wrong.
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