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Difficulty: MediumPhysical Interface and Cabling Types

A network technician is connecting two legacy Cisco switches together using their 100BASE-TX FastEthernet ports. Auto-MDIX is manually disabled on both switch interfaces. Which unshielded twisted-pair (UTP) cable pinout specification is required to establish successful Layer 1 connectivity between these two switches?

  1. A crossover cable with transmit pins 1 and 2 on one connector wired to receive pins 3 and 6 on the opposite connectorAnswer
  2. B
    A straight-through cable with pins 1, 2, 3, and 6 connected directly to pins 1, 2, 3, and 6 on both connectors
  3. C
    A rollover cable with pin 1 on one connector wired to pin 8 on the opposite connector
  4. D
    A crossover cable with pins 4 and 5 swapped with pins 7 and 8 while pins 1, 2, 3, and 6 remain straight through

Answer

A crossover cable with transmit pins 1 and 2 on one connector wired to receive pins 3 and 6 on the opposite connector is required.
Switches default to MDI-X pinouts, transmitting on pins 3 and 6 and receiving on pins 1 and 2. For 100BASE-TX FastEthernet connections between two switches where Auto-MDIX is disabled, pins 1 and 2 on one end must connect to pins 3 and 6 on the other end to link transmit pairs directly to receive pairs.

Step-by-Step Solution

1
Identify the device types being connected and their default interface pinout roles.
Switches use MDI-X pinouts by default, transmitting data on pins 3 and 6 and receiving data on pins 1 and 2.
Connecting identical device types (MDI-X to MDI-X) means both sides transmit on the same pair of pins by default.
2
Determine the impact of disabling Auto-MDIX on both switch interfaces.
Without Auto-MDIX, the interface hardware cannot dynamically swap its internal transmit/receive pin assignments.
Physical pin crossover must be provided by the cabling infrastructure when hardware auto-detection is inactive.
3
Select the proper UTP pinout for 100BASE-TX FastEthernet crossover cabling.
Pin 1 connects to Pin 3, and Pin 2 connects to Pin 6 across the cable connectors.
This bridges the transmit pair of one switch to the receive pair of the opposing switch and vice versa.

Key Concept

Ethernet UTP Cable Pinouts and Auto-MDIX Operations
Estimated Time:1m 0s
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Topics

Physical Interface and Cabling Types

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