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.

• ✓

  Verify that QoS markings and queuing are configured on the switches and routers

  Why this is correct

  Verifying QoS markings and queuing is crucial because Quality of Service mechanisms are designed to prioritize real-time traffic like VoIP over less time-sensitive data. By configuring appropriate DSCP (Differentiated Services Code Point) or CoS (Class of Service) markings, network devices can identify voice packets and place them into high-priority queues. This ensures that even during periods of network congestion, voice packets are forwarded with minimal latency and jitter, preventing the intermittent call drops that occur when voice traffic competes equally with other data.

• ✗

  Check the DNS server for the phone's name resolution

  Why it's wrong here

  Checking the DNS server for phone name resolution is less likely to resolve intermittent call drops during an active conversation. DNS is primarily utilized during the initial call setup phase to resolve FQDNs (Fully Qualified Domain Names) of call managers or other endpoints to their respective IP addresses. Once a call is established and the media stream is flowing, DNS is generally no longer actively involved, meaning ongoing resolution issues would not typically cause intermittent drops in an already connected call.

• ✗

  Replace the patch cables from the phones to the switches

  Why it's wrong here

  Replacing patch cables from phones to switches is generally not the primary solution for intermittent call drops without other symptoms. Physical cabling issues typically manifest as complete link failures, excessive Layer 1/2 errors such as CRC errors, or persistent connectivity problems that are not intermittent. While a severely damaged cable could cause sporadic issues, intermittent call drops during an otherwise stable connection are more indicative of packet loss due to network congestion or misconfiguration at higher layers, rather than a fundamental physical link integrity problem.

  When this WOULD be correct

  A question describing a scenario where IP phones intermittently lose connectivity entirely (not just call drops) and other devices on the same switch port work fine. The correct answer would be to replace patch cables after verifying link lights and cable tester results.

• ✗

  Increase the DHCP lease time for the phones

  Why it's wrong here

  Increasing the DHCP lease time for phones addresses how frequently a device renews its IP address, not the quality of an active voice call. A short lease time might lead to frequent renewal attempts or potential IP conflicts if not managed properly, possibly causing temporary connectivity loss during the renewal process. However, it does not directly influence the quality of voice traffic or cause intermittent packet loss during an active, established conversation, as the IP address remains stable for the duration of the lease.

  When this WOULD be correct

  A question where IP phones are losing their IP addresses and re-registering frequently, causing call drops. For example: 'Users report that VoIP phones disconnect and reconnect every few hours. Which setting should be adjusted?'

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?”

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