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Difficulty: MediumTroubleshooting DNS and Name Resolution Services

A network engineer is troubleshooting a client workstation that cannot connect to an internal web portal using its hostname `srv01.corp.internal`. The engineer executes two `nslookup` queries from the client's command prompt:

text
C:\> nslookup srv01.corp.internal
Server: UnKnown
Address: 192.168.1.1
*** UnKnown can't find srv01.corp.internal: Non-existent domain

C:\> nslookup srv01.corp.internal 10.0.0.53
Server: dc01.corp.internal
Address: 10.0.0.53

Name: srv01.corp.internal
Address: 10.0.0.150

Based on the output above, which of the following are the MOST likely root causes of the name resolution issue on the workstation? (Select TWO.)

  1. The workstation is assigned a default DNS resolver IP address that lacks the internal domain zone information.Answer
  2. B
    The internal domain controller DNS service at 10.0.0.53 is offline or unresponsive to incoming queries.
  3. The local DHCP server scope is misconfigured to distribute a local gateway or public DNS server address instead of the internal DNS server.Answer
  4. D
    The host record for srv01.corp.internal was created as an MX record instead of an A record on the domain controller.

Answer

The workstation is configured with a default DNS server (192.168.1.1, likely a home router or upstream gateway) that does not maintain or forward queries for the internal domain `.corp.internal`. Furthermore, the DHCP server scope distributing network configurations to local clients is misconfigured to pass out 192.168.1.1 rather than the authoritative internal DNS server (10.0.0.53).
The initial query to default DNS server 192.168.1.1 fails because that server does not hold authoritative records for the private zone `corp.internal`. However, explicitly specifying the internal DNS server (10.0.0.53) in the command parameter resolves the hostname successfully. This demonstrates that the internal DNS server is functioning and configured properly with the host A record, but client workstations are using an incorrect default DNS server assigned via DHCP.

Step-by-Step Solution

1
Analyze the default nslookup query output
The workstation automatically queries its configured default server 192.168.1.1, which fails with 'Non-existent domain' (NXDOMAIN).
This confirms that 192.168.1.1 cannot resolve hostnames within the `corp.internal` private namespace.
2
Analyze the explicit nslookup query output targeting 10.0.0.53
When explicitly directed to query server 10.0.0.53, name resolution succeeds immediately and returns IP address 10.0.0.150.
This proves that the internal DNS server is reachable, online, and contains a valid A record for the target host.
3
Deduce the underlying root causes
Identify that the client workstation has an incorrect preferred DNS resolver configured, which is typically distributed dynamically via DHCP scope settings.
Correcting the network adapter's primary DNS setting or updating the DHCP scope options to distribute 10.0.0.53 resolves the issue.

Key Concept

DNS Server Configuration & DHCP Resolver Scopes
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Topics

Troubleshooting DNS and Name Resolution Services

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