220-1101 Networking Practice Question
A network technician is troubleshooting intermittent connectivity issues on a small office network. The issue only occurs for a few minutes at a time, and users lose access to both internal servers and the internet. During the issue, the technician can ping the default gateway from the core switch but not from the router. The router logs show multiple 'Duplicate IP address' errors for the router's LAN interface. Which of the following is the MOST likely cause?
⚠ Common exam trap
CompTIA often tests the distinction between a 'misconfigured DHCP server' (which assigns wrong IPs) and a 'rogue DHCP server' (which causes IP conflicts), trapping candidates who overlook the duplicate IP error in the router logs.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A rogue DHCP server on the network
The 'Duplicate IP address' error on the router's LAN interface indicates that another device on the network is using the same IP address as the router. A rogue DHCP server can assign the router's IP address to another client, causing intermittent connectivity loss. During the conflict, the router cannot respond to traffic, which explains why pinging the default gateway fails from the router but succeeds from the core switch (which may have a cached ARP entry or be on a different VLAN).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
A misconfigured DHCP server on the network
Why it's wrong here
A misconfigured DHCP server might assign invalid IP addresses or overlap with static reservations, but the router logs specifically identify a duplicate of the router's own IP address. That level of specificity points to an address the server was deliberately programmed to hand out, not an accidental configuration error. A truly misconfigured server would produce broader addressing symptoms like wrong gateways or out-of-scope leases, not a single conflict with the router's static IP.
- ✓
A rogue DHCP server on the network
Why this is correct
A rogue DHCP server can hand out the router's IP address to another device, causing an IP conflict that makes the router unreachable intermittently. This matches the symptoms of intermittent connectivity and duplicate IP errors.
- ✗
A spanning tree protocol convergence loop
Why it's wrong here
A spanning tree convergence loop operates at Layer 2, causing broadcast storms, MAC address flapping, and high switch CPU utilization—not duplicate IP address errors. Duplicate IP logs are generated by the IP stack or DHCP client on the router when it detects another device using its address, which is a Layer 3 addressing conflict. While an STP loop could cause intermittent connectivity by overwhelming the network with broadcasts, it would not cause the router to log a duplicate IP conflict, and the absence of flood-related symptoms rules it out.
- ✗
A faulty network cable causing CRC errors
Why it's wrong here
CRC errors cause packet corruption and retransmissions, leading to slow or intermittent connectivity, but they do not result in duplicate IP address errors in router logs. The symptoms point to an IP conflict, not physical layer issues.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1101 exam.