View Full Version : Ethernet at Phyisical Layer
10-23-2011, 05:10 PM
I am a little confused on how the Ethernet layer acts in the physical layer of the OSI model. I am currently reading the 6th edition of the CCNA study guide that Todd Lammle wrote, and to me it just shows the origin of the Ethernet and how to use it etc.
I have also tried and gone through the CCNA objectives in the 6th edition but it did not help.
Please help me, what do the CCNA objectives say about Ethernet working at the physical layer of the OSI model?
And what types of data (if any) is Ethernet responsible for at the Physical Layer?
10-23-2011, 05:28 PM
Ethernet is a standard, IEEE 802.3, and that is your main concern with the Physical Layer for CCNA.
Technically, to say "Ethernet" is to mean 10mb/s, or 802.3i -- if you mean 100mb/s you say "Fastethernet", which is 802.3u. But everyone just says ethernet for short.
The Physical Layer - everything below layer 2, specifies a lot of stuff: encoding, cables, wire pinouts, voltages...etc...
ETHERNET also concerns itself with layer 2, which for CCNA concerns means Framing encapsulation. So Ethernet is really layer 1 and layer 2 related.
What you need to know for the CCNA is basically the physical pinouts of the (ethernet) cable, different cable types (rollover, stp/utp, straight, crossover, serial types) and how an ethernet LAN uses layer 2 addressing (physical mac addressing) as opposed to layer 3 addressing (logical ip addressing).
You should be familiar with default gateways and how data sent out on a wire travels in a LAN - is it staying local or going to the default gateway to be routed elswhere? Know the basics of how a Frame encapsulation works.
10-23-2011, 05:46 PM
Thank you for answering my question... it makes a lot more sense now
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