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Difficulty: MediumPhysical Interface and Cabling Types

A network engineer is interconnecting two legacy network switches via their FastEthernet interfaces. Neither switch interface supports IEEE 802.3ab Auto-MDIX. Which physical cable type and pin mapping must be used on this link to establish Layer 1 connectivity?

  1. A crossover cable with pins 1 and 2 on one end connected to pins 3 and 6 on the opposite endAnswer
  2. B
    A straight-through cable with pins 1 and 2 on one end connected to pins 1 and 2 on the opposite end
  3. C
    A rollover cable with pin 1 connected to pin 8 and pin 2 connected to pin 7
  4. D
    A crossover cable with pins 1 and 2 on one end connected to pins 4 and 5 on the opposite end

Answer

A crossover cable with pins 1 and 2 on one end connected to pins 3 and 6 on the opposite end must be used to interconnect the two switches.
When connecting two switch interfaces (both MDI-X) without Auto-MDIX support, an Ethernet crossover cable is mandatory. In FastEthernet (100BASE-TX), pins 1 and 2 transmit data while pins 3 and 6 receive data. The crossover cable swaps pins 1 and 2 on one connector to pins 3 and 6 on the opposite connector so transmit signals reach the receiver on the other side.

Step-by-Step Solution

1
Identify the device types and port pinouts.
Both switches use MDI-X (Medium Dependent Interface Crossover) port pinouts on their FastEthernet interfaces.
Like network devices (such as switch-to-switch or router-to-PC) operate with identical pin configurations.
2
Evaluate the requirement for crossover wiring when Auto-MDIX is unavailable.
The transmit pair (pins 1 and 2) of one switch must connect to the receive pair (pins 3 and 6) of the opposing switch.
Without Auto-MDIX, the interface cannot automatically reassign transmit and receive functions dynamically.

Key Concept

Ethernet Crossover Cable Pinout Requirements
Estimated Time:1m 0s
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Topics

Physical Interface and Cabling Types

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