A rolled cable looks just like an Ethernet cable. A rolled cable connects the PC’s serial port (using a DB9 to RJ45 adaptor) to the router or switch’s console port. This cable is usually used when configuring one of these devices for the first time.
Download Twisted-Pair Cabling Crossover Cables and more Computer Networks Exams in PDF only on Docsity!Twisted-Pair Cabling Crossover Cables Wiring standards for Ethernet cables using twisted-pair wires Making and testing cables UTP and STP UTP – Unshielded Twisted Pair four pairs are bundled in a plastic “jacket” as a cable Inexpensive most commonly used STP – Shielded Twisted Pair each pair is wrapped in a conductive shield for additional electrical isolation, then bundled in the jacket Pricier, used where required RJ-45 Connectors and Signals This table shows transmit (TX) and receive (RX) pins for a DTE (computer) device – ✦ 10Base-T and 100Base-T “Fast Ethernet” only use two pairs ‣ DTE (active) nodes transmit on pins 1&2, receive on 3&6 ‣ DCE (hubs, switches) receive on pins 1&2, transmit on 3&6 ✦ 1000Base-T “GigE” (and older 100Base-T4) require all four pairs ‣ GigE actually transmits and receives on each pair Pin 10Base-T, 100Base-T 1000Base-T, 10GBase-T 1 Tx data + Tx A + 2 Tx data - Tx A - 3 Rx data + Rx B + 4 unused Tx C + 5 unused Tx C - 6 Rx data - Rx B - 7 unused Rx D + 8 unused Rx D - Straight-Through and Crossover Cables Straight-through cables connect a DTE (e.g., computer) to a DCE (e.g., switch) The same wiring pattern on each end Crossover cables are used to connect one DTE directly to another Transmit-pins 1&2 must be connected to Receive-pins 3&6, and vice-versa For Gigabit crossover, Transmit-pins 4&5 must also be connected to Receive-pins 7&8, and vice-versa What are Rolled Cables? “In the Cisco world, a rolled (or rollover) cable is a cable used to manage a router or switch from the console port of that device.
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