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Difficulty: MediumUtilizing Command-Line Network Troubleshooting Utilities

A network technician executes a command-line DNS query on a workstation to troubleshoot host resolution. The technician receives the following terminal output:

text
Server: resolver.lab.corp
Address: 192.168.1.254

Non-authoritative answer:
Name: fileserver.lab.corp
Address: 10.1.50.12

Which of the following statements correctly interprets the 'Non-authoritative answer' header in this CLI output?

  1. The responding DNS server provided the IP address from its local cache rather than holding the master zone file for the domain.Answer
  2. B
    The client workstation resolved the hostname using its local hosts file because the configured DNS server was unreachable.
  3. C
    The DNS lookup failed because an AAAA record query was submitted instead of a canonical name CNAME record request.
  4. D
    The DNS request was transmitted over UDP port 53 instead of TCP port 53 required for authoritative zone responses.

Answer

The responding DNS server provided the IP address from its local cache rather than holding the master zone file for the domain.
The 'Non-authoritative answer' designation indicates that the DNS server fulfilling the query obtained the host mapping from its cached memory (or via recursive queries to other name servers) rather than maintaining the original authoritative zone database for the domain.

Step-by-Step Solution

1
Analyze the CLI output header and response structure.
The terminal shows that server resolver.lab.corp (192.168.1.254) processed the request for fileserver.lab.corp.
Identifying the responding server verifies that network DNS resolution took place rather than a local file lookup.
2
Evaluate the meaning of the 'Non-authoritative answer' designation in DNS diagnostic tools.
A non-authoritative response indicates the server answered from cached records retrieved from another server.
Authoritative answers only come from the primary or secondary DNS servers hosting the official zone database file for that specific domain.
3
Select the option matching the correct interpretation of DNS cache operations.
The statement explaining that the server answered using cached data from a recursive lookup is correct.
This directly aligns with standard DNS resolver behavior when fulfilling client queries for domains outside their hosted zones.

Key Concept

Interpreting nslookup and DNS command-line utility outputs
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Topics

Utilizing Command-Line Network Troubleshooting Utilities

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