568A and 568B – The number 568 refers to the order in which the individual wires inside a CAT 5 cable are terminated. The only difference between the two standards is that the green and orange pins are terminated to different pins. There is no difference in signal and both the 568A and 568B are used as patch cords for Ethernet connections.
Straight through vs Crossover – A straight through cable uses either the 568A or 568B wiring standard and is used for connecting devices to routers, hubs, switches, etc. An crossover cable is used to connect computing devices together directly (i.e. connecting 2 computers directly together). A crossover cable uses the 568A standard on one end and 568B on the other end.
Rollover – Rollover cable (also known as Cisco console cable) is a type of null-modem cable that is most commonly used to connect a computer terminal to a router’s console port. This cable is typically flat and has a light blue color. It gets the name rollover because the pinouts on one end are reversed from the other, as if the wire had been rolled over and you were viewing it from the other side.
Loopback – A loopback cable redirects the output back into itself and is used for troubleshooting purposes (loopback test). This effectively gives the NIC the impression that it is communicating on a network, since its able to transmit and receive communications.
**Source by wikipedia**
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