Full-duplex Ethernet behavior Which three statements are true about the operation of a full-duplex Ethernet network?

Introduction / Context:
Full-duplex Ethernet allows simultaneous send and receive on twisted-pair or fiber links, eliminating collisions and the need for CSMA/CD. Knowing the operational requirements and consequences of full-duplex is essential for designing modern switched networks with predictable performance.

Given Data / Assumptions:

• (1) No collisions in full-duplex mode.
• (2) A dedicated switch port is required for each full-duplex node.
• (3) Ethernet hub ports are preconfigured for full-duplex mode.
• (4) NIC must check media availability before transmitting in full-duplex.
• (5) Both the NIC and switch port must support full-duplex.

Concept / Approach:

In full-duplex Ethernet, there is no shared medium and no contention; therefore collisions do not occur. Each device uses a dedicated switch port; hubs operate only in half-duplex and cannot be full-duplex. CSMA/CD (carrier sense, collision detect) is disabled in full-duplex, so a NIC does not perform carrier checks before sending. Both link partners must advertise or be configured for full-duplex for it to function properly.

Step-by-Step Solution:

Verification / Alternative check:

On IOS, show interfaces confirms duplex; counters show zero collisions on full-duplex links under normal operation.

Why Other Options Are Wrong:

• Combinations including (3) or (4) are invalid due to hub limitations and the absence of CSMA/CD in full-duplex.
• “5 only” omits other true characteristics.

Common Pitfalls:

• Mismatched duplex settings (auto vs hard-set) lead to late collisions and poor throughput.
• Assuming a hub can operate full-duplex—this is not possible.

Final Answer:

1, 2, and 5