Troubleshooting DNS Resolution Issues with nslookup

N10-009 By islever Editorial Last updated

Given a scenario, troubleshoot common issues with network services.

Short answer

C The administrator should use nslookup to diagnose DNS name resolution failures when IP connectivity works but hostname access fails.

Question

A network administrator receives a report that a user is unable to access several internal resources. The following information is provided during initial troubleshooting:
• Ping is successful to the resources.
• Access to the internet is working.
• Access to resources by IP is successful.
• Other users report no issues.
Which of the following commands would the administrator most likely use to continue troubleshooting?
  1. netstat
  2. nbtstat
  3. nslookup Correct Answer
  4. nnap

Key Takeaways

When ping and IP-based access succeed but hostname access fails, the problem is almost always DNS-related; use nslookup to verify name resolution directly against the DNS server.

Learn how to identify and troubleshoot DNS resolution failures using the nslookup command when network connectivity and IP-based access remain functional.

Common mistake: Choosing netstat is a common mistake because it shows active connections, but it cannot determine if a hostname is resolving correctly to an IP address, which is the core issue here.

Expert Analysis

The scenario presents a classic symptom of a DNS resolution failure. The user can successfully ping resources and access them using their IP addresses, which confirms that the network layer connectivity is intact and routing is functional. Additionally, internet access works, indicating general outbound traffic is not blocked. However, the inability to access internal resources suggests that when the user attempts to use hostnames or domain names, the resolution process fails.

Since other users are unaffected, the issue is localized to this specific workstation's configuration or its interaction with the name resolution service. To diagnose this, the administrator needs a tool that queries Domain Name System (DNS) servers directly to verify if the hostname resolves to the correct IP address.

Option C: nslookup is the correct command. It is a network administration command-line tool available on many computer operating systems for querying the Domain Name System (DNS) to obtain domain name or IP address mapping, or other specific DNS records. By running nslookup <hostname>, the administrator can immediately see if the local DNS server returns an answer or a timeout/error, pinpointing the failure to name resolution rather than network connectivity.

Option A: netstat displays active network connections, routing tables, and interface statistics. While useful for checking open ports or established sessions, it does not help diagnose why a hostname cannot be resolved to an IP address.

Option B: nbtstat displays NetBIOS over TCP/IP statistics and name tables. This is relevant for older Windows networks relying on WINS/NetBIOS but is less standard for modern DNS-based troubleshooting compared to nslookup.

Option D: nnap is not a recognized standard networking command in this context.

Exam Strategy

When analyzing troubleshooting questions, always distinguish between connectivity issues and name resolution issues. If 'ping' and 'IP access' work, rule out physical, data link, and network layer problems. Focus immediately on application layer services like DNS or HTTP. For DNS-specific symptoms (hostname fails, IP works), prioritize tools like nslookup or dig over connection monitors like netstat.

Frequently Asked Questions

What does it mean if ping works but website access fails?

It typically indicates a DNS resolution problem. The network path is valid, but the browser cannot translate the domain name into an IP address.

How does nslookup help in troubleshooting?

nslookup queries a DNS server directly to check if a hostname resolves to an IP address. It helps isolate whether the issue is with the client's cache, the DNS server, or the record itself.

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Community Votes

C
100%

100% of anonymous learners picked answer C. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 1 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 1

  1. ERB14 👍 1 Answered C
    The troubleshooting symptoms show that network layer routing and reachability are completely fine because ping works and access directly via IP address is successful. Since accessing resources by IP works but accessing them by hostname/domain fails, the issue is isolated to DNS name resolution. nslookup is the standard command-line tool used to query DNS servers, verify name resolution, and troubleshoot domain name issues.

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