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Difficulty: MediumNetwork Cable Types and Connectors

A field technician is assembling a custom twisted-pair Ethernet patch cable to connect a workstation to a network switch. The technician terminates one RJ45 connector using the T568A wiring standard and terminates the opposite RJ45 connector using the T568B wiring standard. Which type of cable was created, and how will modern Auto-MDIX-compliant network interfaces handle this connection?

  1. A crossover cable, which modern Auto-MDIX network interfaces will automatically detect and configure to allow successful communicationAnswer
  2. B
    A straight-through cable, which will operate normally without requiring any interface adjustment
  3. C
    A rollover cable, which will prevent link establishment because pin pairs are completely reversed for serial console access
  4. D
    A miswired unusable cable, which causes severe near-end crosstalk (NEXT) that disables link negotiation entirely

Answer

The technician has created a crossover cable because T568A is wired on one end and T568B on the other. Modern network interfaces equipped with Auto-MDIX will detect the reversed transmit and receive pair configuration and dynamically adjust the port signaling to establish full network connectivity.
The correct option correctly identifies that wiring T568A on one connector and T568B on the other end creates a crossover cable. It also accurately states that modern network interfaces equipped with Auto-MDIX will detect the swap of transmit and receive pairs and automatically reconfigure the interface ports so network traffic functions properly.

Step-by-Step Solution

1
Analyze the wiring pinout standards applied to each end of the Ethernet cable
One end is wired with T568A (pin 1 green-white, pin 2 green, pin 3 orange-white, pin 6 orange) and the opposite end is wired with T568B (pin 1 orange-white, pin 2 orange, pin 3 green-white, pin 6 green).
Mixing T568A and T568B across opposite ends of a patch cable transposes transmit (Tx) and receive (Rx) wire pairs.
2
Classify the resulting Ethernet cable type
Transposing pins 1/2 with pins 3/6 defines an Ethernet crossover cable.
Straight-through cables require identical wiring standards on both ends (A-to-A or B-to-B).
3
Determine how modern network interface controllers handle crossover cables
Auto-MDIX (Automatic Medium Dependent Interface Crossover) automatically detects the transposed Tx/Rx signals and configures internal port switching to permit normal link negotiation and data transmission.
Auto-MDIX eliminates the physical requirement of matching straight-through vs crossover cables for switch-to-host or switch-to-switch connections.

Key Concept

T568A vs T568B Pinout Standards and Auto-MDIX Operation
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Topics

Network Cable Types and Connectors

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