220-1101 Networking Practice Question
A user has link lights on a network port but receives very slow file transfers. The switch reports many CRC errors on the port. What is the most likely cause?
⚠ Common exam trap
The trap here is that candidates see link lights and assume the cable is fine, but CRC errors specifically indicate physical-layer corruption that does not prevent link detection.
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
✓
Faulty or damaged Ethernet cable
CRC errors indicate that frames are being corrupted during transmission, which is a classic symptom of a faulty or damaged Ethernet cable. A damaged cable can cause signal degradation, leading to bit errors that the switch detects as CRC mismatches, resulting in retransmissions and slow file transfers.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Faulty or damaged Ethernet cable
Why this is correct
A faulty or damaged Ethernet cable is the correct cause of slow file transfers despite link lights being lit. The link light only confirms electrical continuity at the physical layer, not the integrity of the data frames transmitted. When a cable has kinks, broken pairs, or is subject to electromagnetic interference, the receiver may still detect a carrier signal but the frame check sequence (FCS) will fail, generating CRC errors. These errors force the data link layer to discard frames, triggering retransmissions at higher layers, which dramatically reduces throughput while the link appears active.
- ✗
Unsupported paper size
Why it's wrong here
An unsupported paper size is a printer configuration or driver setting that affects the print job content and media handling inside the printer. It has absolutely no bearing on the Ethernet physical layer or the data link layer, where frame CRC errors are generated. Even if a print job fails or a printer displays an error, the network port on the switch and the attached device still exchange frames normally. Therefore, the paper size setting cannot introduce CRC errors or reduce file transfer speed on the network link.
- ✗
Expired user password
Why it's wrong here
An expired user password is an authentication or authorization issue that manifests at the application layer, typically when the user attempts to log in to the file server or access shared resources. The TCP/IP stack and Ethernet frames are transmitted and received regardless of whether the user later gets an access-denied message. An expired password never causes physical-layer signal degradation or corrupts frame check sequences on the switch port, so it cannot be the reason for CRC errors or slow file transfers while the link lights are on.
- ✗
Incorrect default gateway only
Why it's wrong here
An incorrect default gateway affects routing of packets destined to subnets other than the local one. File transfers within the same local area network are delivered directly via MAC addresses and never traverse the gateway, so a wrong gateway address would not impede them. Even for off-subnet traffic, a wrong gateway typically causes a lack of connectivity or a timeout, not CRC errors or frame corruption on the switch port. Thus, this option cannot explain slow file transfers that are accompanied by link lights being active and CRC errors being present.
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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.