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Difficulty: Very hardWired and Wireless Network Issues

A desktop computer located on an automated factory assembly floor experiences intermittent network drops and heavy packet loss. A network technician reviews the switch interface stats and identifies a rapidly increasing counter for Cyclic Redundancy Check (CRC) errors and frame alignment errors on the wired port. The network cable connecting the workstation runs alongside high-voltage power conduits powering industrial electric motors. Which of the following is the MOST likely cause of these errors?

  1. Electromagnetic interference (EMI) corrupting data frames along the unshielded twisted-pair network cableAnswer
  2. B
    Co-channel overlap between neighboring 2.4 GHz wireless access points deployed near the assembly floor
  3. C
    Failure of the local DNS server to resolve hostnames to IP addresses for workstation applications
  4. D
    An unresponsive DHCP server causing the workstation to assign itself an Automatic Private IP Addressing (APIPA) address

Answer

Electromagnetic interference (EMI) corrupting data frames along the unshielded twisted-pair network cable
Electromagnetic interference (EMI) caused by running unshielded twisted-pair (UTP) cabling next to high-voltage power conduits or heavy electrical motors distorts electrical signals passing through the copper conductors. This signal corruption causes the receiving switch port to detect frame integrity failures, incrementing CRC and frame alignment error counters.

Step-by-Step Solution

1
Analyze the diagnostic symptoms from the switch port output
Identified high counts of Cyclic Redundancy Check (CRC) errors and frame alignment errors on the physical wired link
CRC errors indicate that frames arrived at the switch port corrupted or distorted during transmission
2
Evaluate environmental factors described in the scenario
Noted proximity to high-voltage power conduits and industrial electric motors
High-voltage lines and motors emit strong electromagnetic fields capable of inducing electrical noise into unshielded copper cabling
3
Correlate physical layer noise with CRC error generation
Concluded that EMI is altering signals in transit, leading to frame corruption
Replacing the cable with shielded twisted-pair (STP) cabling or re-routing away from power lines resolves EMI-induced CRC errors

Key Concept

Identifying physical layer wired network issues caused by Electromagnetic Interference (EMI)
Estimated Time:1m 30s
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Topics

Wired and Wireless Network Issues

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