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hackyshank | Cisco CCNA | Module 2 - Layer 1 Physical

By: hackyshank | Related Course: Cisco CCNA | Published: June 14, 2016 | Modified: June 14, 2016
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Notepadphysical layer

physical layer is devices you can touch .

router works at network layer and at a lower layer.

cabling , repeaters , hubs only work at he physical  layer.

X base t

X= speed  =Mbps

base = base band signaling

T= twisted pair

base band signalling , only 1 signal on the wire at one time  vs broadband , where you can have more than 1 signal on the wire.

Twisted pair , 8 wires or 4 pairs of wire have twisted together to make the cable

Ethernet cat 3, 4, 5, 6  3 differs from 5 – 5 means more twists per meter that cat 3 (more twists mean more copper ; more copper means a cleaner signal )

x based cables can be straight through or crossovers.

like device types use crossover cable & unlike devices use straight through .

modem to computer – straight through

router to switch -straight through

switch to switch – cross over and router internet to router internet – crossover

connection of pc ethernet to router ethernet – crossover as well ???

sheilded and un shielded – shielded use where electromagnetic field – used to

serial cable or V.35

roll over cable .


Xbased cable carries signal for 100 meters


HUB is nothing more that multiport repeater

a hub repeats the signal to all ports on the hub except the port the signal originated from.


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