Network+ Exam Objectives 2.4

2.4 Given a scenario, differentiate and implement appropriate wiring standards.

• 568A – 568A is one of the two commonly used standardized 8-wire data network jacks and is commonly used residentially. Generally 568A should be used in residential areas as long as the two inner pairs of 568A are wired the same as a two-line phone jack and that components are internally wired for that specific type.

• 568B – 568B is the second commonly used standardized 8-wire data network jack. T568B is the most prevalent for commercial installations.

• Straight vs. cross-over – Per 10BASE-T and 100BASE-TX Ethernet standards, a wire pair is needed in order for transmission in each direction. This means that the transmit pair of every device has to be connected to the receiving pair of the device on the opposite end. When an end device is connected to a hub or switch, the crossover is internal and takes place in the hub or switch.

In some cases, a device may be connected to another device directly without the use of a hub or switch. When this occurs the crossover must be done externally and the pairs are swapped in the cable. A crossover cable have to be used in order to connect two internally crossed devices, such as two hubs or two switches so that the internal crossovers are nullified.

• Rollover – Sometimes referred to as a Cisco console cable, a rollover is a null modem cable that is most often used to connect a terminal to a router’s console. Rollover cables are generally flat and are often a shade of blue. The name comes from the fact that the pinouts on one end are reversed from those on the other side.

• Loopback – A loopback usually involves the procedures/methods of routing electronic signals, data streams, and other data flows from the originating location back to the same source without any type of intentional modification or processing. Loopback is generally used to test transmission infrastructure.

TCP/IP supports a loopback device which creates a virtual network that is not connected to any sort of hardware. The loopback is implemented through software that is integrated into the systems internal network. Loopback interfaces are used for communication purposes between network software on a computer and server software on the same terminal.