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Mediums Used by IEEE 802.3 Ethernet: What Cannot Be Used?

Mediums Used by IEEE 802.3 Ethernet: What Cannot Be Used?

Verified Sources
Nov 3, 2026

To answer “Which of the following cannot be used as a medium for 802.3 Ethernet?”, we need to know what transmission media the IEEE 802.3 (Ethernet) PHYs are designed to run over. IEEE 802.3 Ethernet is defined for common wired physical media—such as coaxial cable (e.g., thin coax for older Ethernet variants), twisted-pair copper (e.g., 10BASE-T/100BASE-TX/1000BASE-T), and optical fiber (e.g., 10BASE-F/100BASE-FX/1000BASE-SX/LX).3

A microwave link is a wireless/radio medium, not one of the cable media used by 802.3 Ethernet PHY definitions. While Ethernet data can be carried over wireless systems in practice (via bridges/routers), the question asks specifically which option cannot be used as an 802.3 Ethernet medium. The option that does not match the 802.3 supported physical media is:

✅ (ii) A microwave link

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No video included because external video lookup is unavailable in this run.

Footnotes

  1. Ethernet physical layer / 10BASE2 thin coaxial cable overview - Describes classic Ethernet physical layer media including coax variants. ↩

  2. Ethernet physical layer: twisted pair (10BASE-T/100BASE-TX/1000BASE-T) - Summarizes Ethernet PHY links over twisted-pair copper. ↩

  3. Ethernet physical layer: fiber optic (10BASE-F, 100BASE-FX, 1000BASE-SX/LX) - Lists fiber optic Ethernet PHY media and examples. ↩

type="tip" title="Key idea" content="802.3 Ethernet PHYs are defined for wired link media (coax, twisted pair, fiber). Microwave links are wireless radio, so they do not serve as an 802.3 cable-medium PHY."

Determine the Correct Option

  1. 1
    Step 1

    List each option: thin coax, microwave link, twisted pair, fiber.

  2. 2
    Step 2

    802.3 includes variants that use coaxial copper, twisted-pair copper, and fiber optic media.3

    Footnotes

    1. Ethernet physical layer / 10BASE2 thin coaxial cable overview - Describes classic Ethernet physical layer media including coax variants. ↩

    2. Ethernet physical layer: twisted pair (10BASE-T/100BASE-TX/1000BASE-T) - Summarizes Ethernet PHY links over twisted-pair copper. ↩

    3. Ethernet physical layer: fiber optic (10BASE-F, 100BASE-FX, 1000BASE-SX/LX) - Lists fiber optic Ethernet PHY media and examples. ↩

  3. 3
    Step 3

    Microwave links are wireless radio media; they are not listed as standard 802.3 Ethernet physical media.2

    Footnotes

    1. Ethernet physical layer: twisted pair (10BASE-T/100BASE-TX/1000BASE-T) - Summarizes Ethernet PHY links over twisted-pair copper. ↩

    2. Ethernet physical layer: fiber optic (10BASE-F, 100BASE-FX, 1000BASE-SX/LX) - Lists fiber optic Ethernet PHY media and examples. ↩

  4. 4
    Step 4

    The only option that does not fit the 802.3 supported media list is the microwave link (ii).

Keyword-based grounding (quick recall)

  • PHY
  • Medium
  • Twisted-pair
  • Fiber optics
  • Coaxial cable

802.3’s physical layer is associated with these cable/fiber media types rather than a wireless microwave radio hop.3

Footnotes

  1. Ethernet physical layer / 10BASE2 thin coaxial cable overview - Describes classic Ethernet physical layer media including coax variants. ↩

  2. Ethernet physical layer: twisted pair (10BASE-T/100BASE-TX/1000BASE-T) - Summarizes Ethernet PHY links over twisted-pair copper. ↩

  3. Ethernet physical layer: fiber optic (10BASE-F, 100BASE-FX, 1000BASE-SX/LX) - Lists fiber optic Ethernet PHY media and examples. ↩

Common 802.3 Wired Medium Evolution (high level)

Coaxial Ethernet

Legacy

Coax-based Ethernet variants (including thin coax historically)."

Footnotes

  1. Ethernet physical layer / 10BASE2 thin coaxial cable overview - Describes classic Ethernet physical layer media including coax variants. ↩

Twisted-pair copper

Widespread deployments

Twisted-pair 10/100/1000 Mbps Ethernet PHYs dominate typical LAN cabling."

Footnotes

  1. Ethernet physical layer: twisted pair (10BASE-T/100BASE-TX/1000BASE-T) - Summarizes Ethernet PHY links over twisted-pair copper. ↩

Fiber optic Ethernet

Higher reach/speed

Fiber-based PHYs (SX/LX/ZX-style) use optical links for longer distances/high bandwidth."

Footnotes

  1. Ethernet physical layer: fiber optic (10BASE-F, 100BASE-FX, 1000BASE-SX/LX) - Lists fiber optic Ethernet PHY media and examples. ↩

Which options align with IEEE 802.3 physical media?

Conceptual match vs. IEEE 802.3 wired PHY media focus

Common confusion checks

Quick self-test

1 / 3
Question · Term

Which IEEE 802.3 option is NOT a standard medium?

Click to reveal
Answer · Definition

A microwave link (ii). 802.3 PHYs are defined for wired coax/twisted pair/fiber.2

Footnotes

  1. Ethernet physical layer: twisted pair (10BASE-T/100BASE-TX/1000BASE-T) - Summarizes Ethernet PHY links over twisted-pair copper. ↩

  2. Ethernet physical layer: fiber optic (10BASE-F, 100BASE-FX, 1000BASE-SX/LX) - Lists fiber optic Ethernet PHY media and examples. ↩

Knowledge Check

Question 1 of 3
Q1Single choice

Which of the following cannot be used as a medium for 802.3 Ethernet?

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