N10-009 Question 309
Single answer5.3 Given a scenario, troubleshoot common issues with network services.Users in a branch office report that they can browse the internet by website name, but they cannot access the internal file server at filesrv.corp.local. When they try to map a drive using the server name, the request fails immediately. However, mapping a drive using the server's IP address works. A network technician verifies that the file server is online and reachable across the WAN. Which of the following is the MOST likely cause of the problem?
- A
The branch office DHCP scope is handing out the wrong DNS server addresses to clients
- B
The file server has exceeded the maximum number of SMB sessions
- C
The default gateway configured on branch office clients is incorrect
- D
A Layer 2 loop is causing intermittent connectivity to the file server
Show answer and explanation
Correct answer: A
Explanation
This scenario tests troubleshooting of common network services, specifically DNS and DHCP interaction. The key clue is that access by IP address works while access by hostname fails. That usually means the underlying network path and application service are available, but name resolution is failing. Because internet names still resolve, clients are likely using DNS servers that can resolve public records but do not host or forward requests for the internal corp.local zone. In many enterprise environments, DHCP distributes DNS server settings to clients, so an incorrect DHCP scope option can create exactly this issue at a branch office. Best practice is to verify the client IP configuration with tools such as ipconfig /all, confirm the assigned DNS servers, and test name resolution with nslookup or Resolve-DnsName. This aligns with standard DNS troubleshooting guidance and common enterprise design, where internal DNS servers resolve private zones and often forward external queries to public resolvers.
- A. Correct.
Correct. The symptom strongly indicates a DNS resolution problem specific to internal resources. Users can reach internet sites by name, which means name resolution is functioning in some capacity, but they cannot resolve the internal host name filesrv.corp.local. Since accessing the file server by IP address succeeds, IP connectivity and SMB reachability are working. A common real-world cause is DHCP providing public or incorrect DNS servers instead of the organization's internal DNS servers that host the corp.local zone.
- B. Incorrect.
Incorrect. If the file server had exceeded its SMB session limit, users would typically fail whether they connected by hostname or by IP address, because the issue would be with the SMB service accepting connections, not name resolution. The scenario specifically shows that access by IP address works, which rules out this as the most likely cause.
- C. Incorrect.
Incorrect. An incorrect default gateway would commonly affect routing to remote networks, including the file server's IP address. In this scenario, clients can successfully reach the file server when using its IP address, so Layer 3 connectivity is intact. That makes a gateway misconfiguration unlikely.
- D. Incorrect.
Incorrect. A Layer 2 loop usually causes broad network instability such as excessive broadcasts, slow performance, packet loss, or widespread intermittent connectivity. It would not normally produce a clean and repeatable pattern where hostname access fails but direct IP access succeeds. That pattern points much more directly to DNS.