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.

• ✗

  The DHCP server has exhausted its address pool.

  Why it's wrong here

  If the DHCP server had genuinely exhausted its address pool, it would be unable to offer IP addresses to *any* new client requesting a lease on that specific VLAN or scope. This would manifest as multiple users or devices on the same network segment failing to obtain DHCP leases, not just an isolated incident with one user's computer. The problem would be widespread across the subnet, indicating a server-side resource limitation rather than a client-specific issue.

  When this WOULD be correct

  This option would be correct in a scenario where multiple users on the same VLAN are unable to obtain DHCP leases, and the DHCP server logs indicate no available addresses. The question would specify that all users are affected.

• ✗

  The switch port is in a blocked state due to a spanning tree loop.

  Why it's wrong here

  A spanning tree protocol (STP) blocked state is a normal operational state to prevent network loops, not necessarily indicative of an active loop. If a switch port were blocked by STP, no traffic, including DHCP requests, would pass through it, effectively making the link appear completely non-functional for all protocols. However, a user's computer typically wouldn't even attempt DHCP if the physical link was entirely non-functional due to a blocked port. Furthermore, if an active loop *were* occurring, it would cause network-wide broadcast storms and severe performance degradation, affecting far more than just one user's DHCP process.

• ✓

  The user's computer has not authenticated via 802.1X and is placed in a restricted VLAN.

  Why this is correct

  With 802.1X, unauthenticated devices are often placed in a restricted VLAN that may not include the DHCP server or have limited access. This explains why the computer gets an APIPA address while other devices on the same physical port (if authenticated) work normally.

• ✗

  The network cable is faulty.

  Why it's wrong here

  A faulty network cable would typically result in a complete loss of link connectivity, indicated by no link lights on the network interface card (NIC) or switch port, or severe packet loss and errors. If the computer is able to attempt DHCP, it implies that a physical layer connection has been established and basic communication is possible, even if the DHCP request isn't successful. While a *partially* faulty cable could cause intermittent issues, a complete inability to obtain a DHCP lease without other symptoms like link flapping or no link suggests a higher-layer problem.

  When this WOULD be correct

  In a scenario where a user's computer shows 'Network cable unplugged' or intermittent disconnects, and other devices on the same port also fail, a faulty cable would be the likely cause.

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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