Crossover cable pinouts

In practice, it does not matter if non-crossover Ethernet cables are wired as T568A or T568B, just so long as both ends follow the same wiring format. Typical commercially available "pre-wired" cables can follow either format depending the manufacturer.

What this means is that one manufacturer's cables are wired one way and another's the other way, yet both are correct and will work. In either case, T568A or T568B, a normal (un-crossed) cable will have both ends wired according to the layout in the Connection 1 column.

Although the Gigabit crossover is defined in the Gigabit Ethernet standard, in practice all Gigabit PHYs feature an auto-MDIX capability and are designed for compatibility with the existing 100BASE-TX crossovers. The IEEE-specified Gigabit crossover is generally seen as unnecessary.Certain equipment or installations, including those in which phone and/or power are mixed with data in the same cable, may require that the "non-data" pairs 1 and 4 (pins 4, 5, 7 and 8) remain un-crossed.

December 6, 2011

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