Wednesday, January 29, 2014

Ethernet CrossOver Cable Tutorials And Notes

CrossOver Cable Making

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Source:- Google.com.pk

ITKiDuniyaa Define Ethernet CrossOver Cable?

An Ethernet crossover cable is a type of Ethernet cable used to connect computing devices together directly. Normal straight through or patch cables were used to connect from a host network interface controller (a computer or similar device) to a network switch, hub or router. A cable with connections that "cross over" was used to connect two devices of the same type: two hosts or two switches to each other. Owing to the inclusion of Auto-MDIX capability, modern implementations of the Ethernet over twisted pair standards usually no longer require the use of crossover cables.

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Overview

The 10BASE-T and 100BASE-TX Ethernet standards use one wire pair for transmission in each direction. This requires that the transmit pair of each device be connected to the receive pair of the device on the other end. When a terminal device is connected to a switch or hub, this crossover is done internally in the switch or hub. A standard straight through cable is used for this purpose where each pin of the connector on one end is connected to the corresponding pin on the other connector.

One terminal may be connected directly to another without the use of a switch or hub, but in that case the crossover must be done in the cabling. Since 10BASE-T and 100BASE-TX use pairs 2 and 3, these two pairs must be swapped in the cable. This is a crossover cable. A crossover cable may also be used to connect two hubs or two switches on their upstream ports.

Because the only difference between the T568A and T568B pin/pair assignments are that pairs 2 and 3 are swapped, a crossover cable may be envisioned as a cable with one modular connector following T568A and the other T568B (see Jack crossover wiring). Such a cable will work for 10BASE-T or 100BASE-TX. Gigabit Ethernet (and an early Fast Ethernet variant, 100BASE-T4) use all four pairs and also requires the other two pairs (1 and 4) also to be swapped.

The polarity of each pair is not swapped, but the pairs crossed as a unit: the two wires within each pair are not crossed.

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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 on 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.

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IT KI DUNIYAA | Reading for information | Needs of All Students And learners

Automatic crossover

Introduced in 1998, this made the distinction between uplink and normal ports and manual selector switches on older hubs and switches obsolete. If one or both of two connected devices has the automatic MDI/MDI-X configuration feature, there is no need for crossover cables.

Although Auto-MDIX was specified as an optional feature in the 1000BASE-T standard, in practice it is implemented widely on most interfaces.

Besides the eventually agreed upon Automatic MDI/MDI-X, this feature may also be referred to by various vendor-specific terms including: Auto uplink and trade, Universal Cable Recognition and Auto Sensing.

ITKiDuniyaa Explains Ethernet Crossover Cable In Simple Words

Definition: A crossover cable directly connects two network devices of the same type to each other over Ethernet. Ethernet crossover cables are commonly used when temporarily networking two devices in situations where a network router, switch or hub is not present.

Compared to standard Ethernet cables, the internal wiring of Ethernet crossover cables reverses the transmit and receive signals. The reversed color-coded wires can be seen through the RJ-45 connectors at each end of the cable:

    Standard cables have an idential sequence of colored wires on each end
    Crossover cables have the 1st and 3rd wires (counting from left to right) crossed, and the 2nd and 6th wires crossed


An Ethernet crossover cable will also feature the name "crossover" stamped on its packaging and wire casing.

Ethernet crossover cables should only be used for direct network connections. In particular, attempting to connect a computer to a hub with a crossover cable will prevent that network link from functioning. Home broadband routers have become an exception to this rule: modern consumer routers contain logic to automatically detect crossover cables and allow them to function with other types of Ethernet devices.

ITKiDuniyaa Explains Ethernet Crossover Cable In Short Words

Similar to a null-modem cable, with the exception that the crossover cable is used for Ethernet connections, where the CTS (clear to send) and RTS (ready to send) lines are crossed over. On a null-modem cable the Tx (transmit) and Rx (Recieve) lines are crossed over.

How To Make An Ethernet Cross-Over Cable Urdu [Tutorial Provided By ITKiDuniyaa]

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ITKiDuniyaa Cross-over Cable Step 1
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ITKiDuniyaa Cross-over Cable Step 2
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