TIA/EIA 568B wiring standard.
Ethernet (10Base-T) and Fast Ethernet (100Base-TX) on Cat 5.
Hence, an Ethernet and Fast Ethernet cross-over cable is implemented by crossing pins 1 to 3, 2 to 6, 3 to 1, and 6 to 2 as shown below.
Ethernet and Fast Ethernet cross-over cable.
The 1000Base-T Gigabit Ethernet standard uses all four pairs of the Cat 5e cable. Each pair is used to transmit and receive data simultaneously, known as Dual-Duplex transmission. Basically, this is a technique where it is possible to distinguish the direction a signal is traveling.
The figure below shows the difference between 100Base-TX and 1000Base-T signaling. The 10Base-T and 100Base-TX uses separate pairs for transmit and receive. Hence it is necessary to wire for a specific type of connection. The 1000Base-T transmits and receives simultaneously on each pair. Since there is no difference in the wires used to transmit and receive signals for any device, the standard patch cable, wired straight though, can connect a Gigabit Ethernet adapter to either a switch/hub port or another adapter.
Note that it still should be possible to use a Fast Ethernet cross-over cable to connect two Gigabit adapters if the adapter auto detects the best supported operating mode. But both the adapters should drop to 100Mbps.
Published with the express written permission of the author. Copyright 2002 Joe Chang. All Rights Reserved.
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