N10-009 Network Troubleshooting Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  Incorrect DNS configuration on the workstation

  Why it's wrong here

  DNS (Domain Name System) is responsible for translating human-readable domain names (e.g., google.com) into numerical IP addresses. If a workstation's DNS configuration is incorrect, it would fail to resolve hostnames, preventing access to websites by name. However, when a user attempts to ping an external resource using its direct IP address, DNS resolution is entirely bypassed, meaning an incorrect DNS setting would not hinder the ability to reach an external IP.

  When this WOULD be correct

  A user can access the internet by IP but not by domain name. Pinging 8.8.8.8 succeeds, but pinging google.com fails. The technician checks DNS settings and finds the workstation is configured with an invalid DNS server.

• ✓

  Missing default route on the router

  Why this is correct

  When a router receives a packet for a destination not on its directly connected networks or within its specific routing table entries, it consults its default route. If this route (often 0.0.0.0/0) is absent, the router has no "gateway of last resort" and will drop all traffic intended for external networks, such as the internet. This directly prevents any device behind that router from accessing resources outside the local network, including public IP addresses.

• ✗

  Duplicate IP address on the local network

  Why it's wrong here

  A duplicate IP address on a local network occurs when two devices are configured with the same IP, leading to conflicts and intermittent connectivity problems for both. While this can disrupt network communication, it typically manifests as sporadic disconnections or difficulty reaching local resources, and often a device can still ping its default gateway. The primary symptom of being unable to reach any external IP address consistently points away from a local IP conflict and towards a broader routing failure.

  When this WOULD be correct

  This would be correct in a scenario where a user reports intermittent connectivity or 'address conflict' errors, and the technician finds that pinging the default gateway sometimes fails or returns inconsistent results, with ARP table showing multiple MAC addresses for the same IP.

• ✗

  Proxy server configuration is required

  Why it's wrong here

  Proxy servers operate at the application layer (Layer 7) of the OSI model, primarily handling specific protocols like HTTP, HTTPS, and FTP. While they can control web access, they do not process lower-layer protocols such as ICMP, which is used by the ping utility. Therefore, the absence or misconfiguration of a proxy server would not prevent a device from successfully pinging an external IP address directly, as ping traffic bypasses proxy mechanisms.

  When this WOULD be correct

  A proxy server configuration would be the correct answer if the question stated that the user can access internal resources but not external websites, and pinging public IPs fails while pinging internal IPs succeeds, with the firewall blocking direct outbound traffic and requiring proxy settings for internet access.

Option-by-option analysis

Why each answer is right or wrong

Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.

Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”