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what is the official specification for 100BASE-T4

I have consulted a number of references (Cisco Press books, CCO, exam guides) and some descriptions are vague while others are outright contradictory. What is the duplex rating for 100Base-T4 and what category of cable does it require. I understand that it requires 4 pair (rather than 2 like -TX) and the 100 in 100Base means 100Mbps. My understanding is that it is capable of full duplex and works over cat 3, 4, and 5. Also, has this specification been revised recently? If so is there one correct answer for production and another for Cisco CCNP exams?

  • Other Network Infrastructure Subjects

Re: what is the official specification for 100BASE-T4

IEEE 802.3u specifies the following different physical layers for 100BASE-T:

100BASE-TX—100BASE-T, half and full duplex over Category 5 unshielded twisted-pair (UTP), Electronics Industry Association/Telecommunications Industry Association [EIA/TIA]-568-compliant cable

100BASE-FX—100BASE-T, half and full duplex over optical fiber

100BASE-T4—100BASE-T, half and full duplex over Category 3, 4, or 5 UTP or shielded twisted-pair (STP) cabling with four pairs; also called 4T+ or T2, which is 2-pair UTP over Category 3 cable.

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