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Difficulty: MediumWired and Wireless Network Issues

A field technician installs a IP-based security camera at the far end of a logistics warehouse. The camera is connected back to a PoE switch port using a single continuously run Category 6 Ethernet cable measuring 120 meters (394 feet). Upon powering on the system, the camera intermittently reboots, drops packets, and experiences severe video signal degradation. Testing the cable run with a standard wire mapper shows that all eight pin continuity connections match the T568B termination standard. Which of the following is the MOST likely cause of the network instability?

  1. The Ethernet cable run length exceeds the 100-meter maximum distance specification for copper twisted-pair cabling.Answer
  2. B
    The camera's network card has defaulted to an APIPA address because the network interface card link lights are unlit.
  3. C
    The DHCP server on the local network segment is improperly acting as a DNS server for the security camera.
  4. D
    The Category 6 cable is suffering from adjacent channel overlap on the 2.4 GHz wireless frequency band.

Answer

The Ethernet cable run length exceeds the 100-meter maximum distance specification for copper twisted-pair cabling.
The standard maximum distance specification for copper Ethernet cabling (Cat 5e, Cat 6, Cat 6a) is 100 meters (328 feet), typically configured as 90 meters of solid horizontal cabling and 10 meters of stranded patch cables. A 120-meter cable run causes severe signal attenuation (loss of signal strength) and Power over Ethernet (PoE) voltage drop, leading to packet loss, latency, and intermittent device reboots.

Step-by-Step Solution

1
Analyze the physical layer specifications provided in the scenario.
The Category 6 Ethernet cable run length is 120 meters (394 feet).
Standard Ethernet specifications (802.3) limit copper twisted-pair cable runs (including patch cables and horizontal cabling) to a maximum length of 100 meters (328 feet).
2
Evaluate the reported symptoms against physical distance limitations.
Signals traveling over 100 meters suffer from severe attenuation and voltage drop over Power over Ethernet (PoE).
Attenuation degrades data packets causing loss, while voltage drop causes the camera to intermittently lose power and reboot.
3
Select the root cause matching the physical layer violation.
Exceeding the 100-meter maximum distance limitation is the root cause.
A Ethernet repeater, PoE extender, or fiber optic link must be used for runs exceeding 100 meters.

Key Concept

Ethernet Maximum Cable Length Limitations and Attenuation
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Topics

Wired and Wireless Network Issues

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