008 Understanding Ethernet

7/24/2019 008 Understanding Ethernet

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2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-1

Building a Simple Network

nderst!nding "thernet


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Local Area Network


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LAN Components Com$%ters

& 'Cs

& Servers

Interconnections

& NICs

& (edi!

Net)or* devices

& +%s

& S)itches

& o%ters

'rotocols

& "thernet

& I'

& A'

& D+C'


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Functions of a LAN

D!t! !nd !$$lic!tions

Sh!re reso%rces

'rovide comm%nic!tion $!th to other net)or*s


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LAN Sizes


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Ethernet Evolution


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LAN Standards


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CSMAC!


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Ethernet Frame Structure



Communicating "ithin the LAN



MAC Address Components



MAC Addresses


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Summar#

A 3AN is ! net)or* th!t is loc!ted in ! limited !re!, )ith thecom$%ters !nd other com$onents th!t !re $!rt o4 this net)or*loc!ted rel!tively close together.

eg!rdless o4 its si5e, sever!l 4%nd!ment!l com$onents !re

re6%ired 4or the o$er!tion o4 ! 3AN, incl%ding com$%ters,interconnections, net)or* devices, !nd $rotocols.

3ANs $rovide oth comm%nic!tion !nd reso%rce-sh!ring4%nctions 4or their %sers.

3ANs c!n e con4ig%red in v!rio%s si5es, to !ccommod!teenvironments 4rom S+ to enter$rise.



Summar# $Cont%&

"thernet )!s origin!lly develo$ed in the 170s y D"C, Intel, !nd 8ero9,!nd )!s c!lled DI8 "thernet. :hen ! )or*gro%$ o4 this ody ;re4erred to!s I""" 02.#< de4ined ne) st!nd!rds 4or "thernet in the mid-10s tode4ine "thernet-li*e net)or*s 4or $%lic %se, the st!nd!rds )ere c!lled"thernet 02.# !nd 02.2.

"thernet 3AN st!nd!rds s$eci4y c!ling !nd sign!ling !t oth the$hysic!l !nd d!t! lin* l!yers o4 the SI model.

St!tions on ! CS(A=CD 3AN c!n !ccess the net)or* !t !ny time. >e4oresending d!t!, CS(A=CD st!tions listen to the net)or* to determine)hether it is !lre!dy in %se. I4 it is in %se, they )!it. I4 the net)or* is not

in %se, the st!tions tr!nsmit. A collision occ%rs )hen t)o st!tions listen4or net)or* tr!44ic, he!r none, !nd tr!nsmit sim%lt!neo%sly.


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Summar# $Cont%&

An "thernet 4r!me consists o4 4ields, incl%ding $re!mle, st!rt-o4-4r!me delimiter, destin!tion !ddress, so%rce !ddress, ty$e=length,d!t! !nd $!d, !nd 4r!me chec* se6%ence.

?here !re three m!@or *inds o4 comm%nic!tions in net)or*s

%nic!st, in )hich ! 4r!me is sent 4rom one host !ddressed to ones$eci4ic destin!tionB ro!dc!st, in )hich ! 4r!me is sent 4rom one!ddress to !ll other !ddressesB !nd m%ltic!st, in )hich !destin!tion !ddresses ! s$eci4ic gro%$ o4 devices.

?he !ddress %sed in !n "thernet 3AN is the me!ns y )hich d!t!

is directed to the $ro$er receiving loc!tion.



Summar# $Cont%&

?he (AC s%l!yer h!ndles $hysic!l !ddressing iss%es, !nd the$hysic!l !ddress is ! -it n%mer %s%!lly re$resented inhe9!decim!l 4orm!t.


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008 Understanding Ethernet