Question

Difficulty: EasyTroubleshooting DNS and Name Resolution Services

A network administrator runs the following command on a host experiencing name resolution failures:

C:\> nslookup app.corp.local 192.168.1.10
Server: dns01.corp.local
Address: 192.168.1.10

*** dns01.corp.local can't find app.corp.local: Non-existent domain

Based on the output, which TWO of the following represent plausible root causes for this error? (Select TWO.)

  1. An A record for the hostname app.corp.local is missing from the forward lookup zone on the DNS server.Answer
  2. The queried hostname app.corp.local contains a typographical error or does not match the configured domain name record.Answer
  3. C
    The DNS server IP address is configured as the local host's default gateway address on TCP port 53.
  4. D
    The client network router failed to convert UDP port 53 DNS queries into TCP port 80 HTTP packets.

Answer

The correct root causes are that an A record for app.corp.local is missing from the DNS server's forward lookup zone, and that the queried hostname contains a typographical error or does not match the record.
The nslookup utility successfully established contact with DNS server 192.168.1.10, but received an NXDOMAIN response. This demonstrates that network layer connectivity is operational, but the DNS zone database lacks an A/AAAA record for the queried name, or the user queried a misspelled domain name.

Step-by-Step Solution

1
Analyze the nslookup command output.
The command successfully communicated with the specified DNS server at IP address 192.168.1.10192.168.1.10.
The output returns the server name and address, indicating network connectivity to the DNS service on port 53 is functional.
2
Evaluate the specific error message returned by the resolver.
The server responded with 'can't find app.corp.local: Non-existent domain' (NXDOMAIN).
NXDOMAIN confirms the DNS server processed the query but could not find a matching host record in its database.
3
Identify valid causes for an NXDOMAIN response.
The missing host record (A record) on the DNS zone or an incorrect host name query are the correct explanations.
Both causes directly explain why an authoritative DNS server returns a non-existent domain error.

Key Concept

Troubleshooting DNS NXDOMAIN Errors and Host Record Misconfigurations
Rate this question