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Difficulty: EasyTroubleshooting DNS and Name Resolution Services

A administrator executes a command-line test on a workstation to verify name resolution for an internal web server named `portal.local`. The command output is shown below:

C:\> nslookup portal.local
Server: dns1.contoso.com
Address: 10.0.0.10

*** dns1.contoso.com can't find portal.local: Non-existent domain

Which of the following is the most likely cause of this error?

  1. The DNS server is missing an active host (A) record for portal.local.Answer
  2. B
    The workstation resolver cache is corrupted and returning stale data.
  3. C
    An outbound firewall is blocking TCP port 53 traffic to the server.
  4. D
    The hostname requires a Mail Exchanger (MX) record for standard name resolution.

Answer

The DNS server is missing an active host (A) record for portal.local.
The output explicitly shows a successful query transaction with the DNS server at 10.0.0.10, which replied with 'Non-existent domain' (NXDOMAIN). This confirms that network communication with the DNS server is working, but the server has no host (A) record registered for portal.local.

Step-by-Step Solution

1
Analyze the nslookup command output
The target DNS server at 10.0.0.10 answered the query directly with 'Non-existent domain' (NXDOMAIN).
An explicit NXDOMAIN response indicates that network connectivity and DNS service availability are functional.
2
Determine the cause of the NXDOMAIN response
The DNS zone database on the server does not contain a valid mapping for portal.local.
Standard hostname resolution requires a host (A or AAAA) record entry in the DNS server database.

Key Concept

Interpreting DNS Lookup Output and NXDOMAIN Error Response
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Topics

Troubleshooting DNS and Name Resolution Services

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