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220-1201 Practice Question: A technician is troubleshooting a network where a…
A technician is troubleshooting a network where a user's PC has an IP address of 169.254.12.34. The PC is connected to a switch that is uplinked to a router with DHCP enabled. What is the most likely cause?
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
✓
The Ethernet cable between the PC and the switch is faulty.
An APIPA address (169.254.x.x) indicates the PC failed to get a DHCP lease. Since the router has DHCP enabled, the issue is likely a bad Ethernet cable or a port problem preventing communication with the DHCP server.
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 is out of IP addresses.
Why it's wrong here
If a DHCP server's address pool (scope) is exhausted, it would not be able to offer an IP address to a requesting client. While this scenario could eventually lead to a client self-assigning an APIPA address due to a lack of a DHCP Offer, it implies the client *could* reach the server. A more direct cause for an APIPA address is when the client cannot establish *any* communication with a DHCP server, preventing it from even receiving a DHCP Offer or NAK.
- ✓
The Ethernet cable between the PC and the switch is faulty.
Why this is correct
A faulty Ethernet cable, such as one with a broken wire or poor connection, would prevent the PC from establishing a physical layer (Layer 1) link with the network switch. Without this fundamental connectivity, the PC cannot send its DHCP Discover broadcast packet to reach the DHCP server. Consequently, after multiple attempts and timeouts, the operating system will resort to self-assigning an Automatic Private IP Addressing (APIPA) address in the 169.254.0.0/16 range.
- ✗
The PC's DNS settings are incorrect.
Why it's wrong here
Incorrect DNS settings on a PC would primarily affect its ability to resolve hostnames to IP addresses, impacting web browsing or accessing network resources by name. DNS operates at a higher layer (Application Layer) than the process of obtaining an IP address via DHCP. The failure to acquire an IP address and the subsequent self-assignment of an APIPA address occurs *before* DNS settings would even be utilized or become relevant.
- ✗
The router's firewall is blocking DHCP requests.
Why it's wrong here
While a router's firewall *could* theoretically block DHCP requests (which use UDP ports 67 and 68), this is highly unlikely in a typical network configuration. Routers are designed to facilitate network communication, and blocking essential services like DHCP by default would render the network unusable for most clients. Furthermore, if the router's firewall were blocking DHCP, *all* clients attempting to obtain an IP address through that router would experience the same issue, not just a single user's PC.
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Related to this question
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Network Configuration: IP, DNS, DHCP
Key term
Automatic Private Internet Protocol Addressing
A fallback method used by a device to automatically assign itself an IP address when it cannot obtain one from a DHCP server.
Key term
Router
A router is a networking device that connects different networks together and directs data traffic between them by choosing the best path for data to travel.
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Same concept, more angles
1 more way this is tested on 220-1201
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. During a network upgrade, a new switch is installed. After connecting all devices, one workstation cannot obtain an IP address via DHCP, while all other workstations on the same switch work fine. What is the first step to troubleshoot this issue?
easy- A.Replace the network cable.
- ✓ B.Check if the network cable is securely connected and the link lights are on.
- C.Restart the DHCP service on the router.
- D.Assign a static IP address to the workstation.
Why B: When a single workstation fails to get an IP address but others succeed, the problem is likely with that workstation or its cable. Checking the physical connection is the quickest and easiest first step before moving to software or configuration checks.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1201 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 220-1201 exam.