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220-1201 Practice Question: A customer reports that their new Gigabit…
A customer reports that their new Gigabit Ethernet connection is only achieving 100 Mbps speeds. The cable run is 75 meters through a drop ceiling and uses a Cat5e cable. What is the most likely cause of the speed limitation?
⚠ Common exam trap
CompTIA A+ often tests the misconception that cable length is the primary limiting factor for Gigabit Ethernet, when in fact Cat5e supports up to 100 meters, and the real issue is often the cable category or a fallback negotiation.
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 cable is actually Cat5, not Cat5e.
Cat5e is rated for Gigabit Ethernet (1000BASE-T) up to 100 meters. However, if the cable is actually Cat5 (not Cat5e), it is only certified for 100 Mbps (100BASE-TX) at that distance. The 75-meter run is within spec for Cat5e, so the most likely cause is that the installed cable is Cat5, which cannot reliably support 1000BASE-T.
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 cable is too long for Cat5e.
Why it's wrong here
Cat5e cabling is specifically engineered to reliably support Gigabit Ethernet (1000BASE-T) speeds over distances up to 100 meters (328 feet). Since the customer's cable run is stated as 75 meters, it falls well within the maximum specified length for Cat5e to achieve its rated gigabit performance. Therefore, the physical length of the cable is not the limiting factor for speed in this particular scenario.
- ✓
The cable is actually Cat5, not Cat5e.
Why this is correct
Standard Category 5 (Cat5) Ethernet cable is only certified to support network speeds up to 100 Mbps (100BASE-TX) due to its less stringent specifications for crosstalk and impedance. In contrast, Category 5e (Cat5e) cable introduces enhanced specifications, particularly for crosstalk performance, enabling it to reliably support Gigabit Ethernet (1000BASE-T) up to 1000 Mbps. If a Cat5 cable is mistakenly used where Cat5e is required for a gigabit connection, the link will negotiate down to its maximum supported speed of 100 Mbps, directly explaining the customer's reported speed limitation.
- ✗
The cable is shielded and causing interference.
Why it's wrong here
Shielded Twisted Pair (STP) cables are designed with an additional metallic layer specifically to *reduce* electromagnetic interference (EMI) and radio frequency interference (RFI) from external sources, thereby protecting signal integrity. While improper grounding of shielded cables can sometimes introduce noise, the shielding itself is a protective feature, not a cause of interference or speed limitations. Shielded cables can fully support Gigabit Ethernet speeds and are often preferred in electrically noisy environments to maintain performance.
- ✗
The network switch port is faulty.
Why it's wrong here
While a faulty network switch port *could* certainly cause connectivity or speed issues, it typically manifests as no connection at all, intermittent drops, or a complete failure to negotiate a link. In this scenario, the customer reports a *new* gigabit connection that is not achieving expected speeds, implying a stable but slower link. This symptom points more directly to a component like the cable itself, which is physically incapable of supporting the higher speed, rather than a completely malfunctioning port.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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