Definition of 100BaseTX in The Network Encyclopedia.

What is 100BaseTX?

100BaseTX is a type of standard for implementing Fast Ethernet networks. 100BaseTX is based on 802.3u, which is an extension of the 802.3 specifications of Project 802 developed by the IEEE. 100BaseTX and a related standard, 100BaseFX, are sometimes collectively referred to as 100BaseX.

100BaseTX network.

How 100BaseTX Work?

100BaseTX networks are wired together in a star topology using unshielded twisted-pair (UTP) cabling or shielded twisted-pair (STP) cabling and 100-Mbps hubs or Ethernet switches. If UTP cabling is used (which is the most common scenario), it must be category 5 cabling (cat5 cabling) or enhanced category 5 cabling. 100BaseTX uses two pairs of wires in twisted-pair cabling, with one pair of wires used for transmission and the other used for reception. In this fashion, with appropriate equipment, 100BaseTX is capable of supporting both the normal half-duplex Ethernet and the newer full-duplex Ethernet signaling technologies.

The maximum length of any segment of UTP cabling connecting a station to a hub is 100 meters. This ensures that round-trip signaling specifications are met, since violating these specifications can produce late collisions that disrupt network communications. The Electronic Industries Alliance/Telecommunications Industry Alliance (EIA/TIA) recommends only 90 meters of cabling between the station (computer) and the wiring closet, allowing up to 10 meters more of cabling for patch cables used to connect patch panels to hubs or switches. The pinning of the RJ-45 connectors used for 100BaseTX wiring is the same as for 10BaseT wiring.


Make sure all your cabling, connectors, and patch panels are fully cat5-compliant. Make sure that when UTP cabling is connected to patch panels, wall plates, or connectors, the wires are not untwisted more than half an inch at the termination point.

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