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grieger | Cisco CCNA | Module 2 - Layer 1 Physical

By: grieger | Related Course: Cisco CCNA | Published: April 2, 2018 | Modified: April 3, 2018
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NotepadPhysical Layer

Physical layers are things you can touch. these consists of 1)cable, 2)repeaters and 3)hubs. 

The cable is x_base_t where x is the speed per second, base is the baseband signal where there is only one signal on the wire at a time and t means it is a twisted pair. (4×2 pair for 8 wires) the higher the number for t means more twists which means more copper wire which means a cleaner signal.

The cable comes in 2 types. Straight through and Crossover. Straight through is used for unlike devices like a computer to a switch. Crossover is used for like devices like a switch to switch or router to router. A PC internet port to router internet port would also use a crossover cable.

Cable come unshielded  like the ones used at home and shielded where the cable is exposed to with high EMI/RFI.

Repeaters are use to extend the signal where the cable is 100 meters or more.

Hubs are just multi port repeaters used to send signal to several different devices. A hub will send or flood signal to all ports except the one that the signal is entering the hub on.


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