ITN InstructorPPT Chapter 5 Cisco

8/18/2019 ITN InstructorPPT Chapter 5 Cisco

1/67

© 2008 Cisco Systems, Inc. All r ights reserved. Cisco ConfidentialPresentation_ID

Cha!ter "#$thernet

Introduction to Networks


2/67

Presentation_ID 2© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

Chapter 6 : Objectives

In this cha!ter, yo% &ill learn to#Descri'e the o!eration of the $thernet s%'layers.

Identify the ma(or fields of the $thernet frame.

Descri'e the !%r!ose and characteristics of the $thernet)AC address.

Descri'e the !%r!ose of A*P.

$+!lain ho& A*P re %ests im!act net&or- and host

!erformance.$+!lain 'asic s&itching conce!ts.

Com!are fi+ed config%ration and mod%lar s&itches.

Config%re a ayer / s&itch.


3/67

Presentation_ID /© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

Ethernet

Introduction

his cha!ter e+amines the characteristics and o!eration of$thernet as it has evolved from a shared media, contention1'ased data comm%nications technology to today s high'and&idth, f%ll1d%!le+ technology.


4/67


Chapter 5

".0 Introd%ction". $thernet Protocol".2 Address *esol%tion Protocol

"./ A4 S&itches".3 S%mmary


5/67

Presentation_ID "© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

5.1

Ethernet Protocol


6/67


Ethernet Operation

C and !"C #ubla$ers

$thernet 67 )ost &idely %sed A4 technology7 !erates in the data lin- layer and the !hysical layer7 9amily of net&or-ing technologies that are defined in the I$$$ 802.2

and 802./ standards7 S%!!orts data 'and&idths of 0, 00, 000, 0,000, 30,000, and

00,000 )'!s : 00 ;'!s<

$thernet standards 6

7 Define ayer 2 !rotocols and ayer technologies7 &o se!arate s%' layers of the data lin- layer to o!erate 1 ogical

lin- control : C< and the )AC s%'layers


7/67Presentation_ID =© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

Ethernet Operation

C and !"C #ubla$ers


8/67Presentation_ID 8© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

Ethernet Operation

C and !"C #ubla$ers

C

7 >andles comm%nication 'et&een %!!er and lo&er layers

7 a-es the net&or- !rotocol data and adds control

information to hel! deliver the !ac-et to the destination!"C

7 Constit%tes the lo&er s%'layer of the data lin- layer

7 Im!lemented 'y hard&are, ty!ically in the com!%ter 4IC7 &o !rimary res!onsi'ilities#

7 Data enca!s%lation7 )edia access control


9/67Presentation_ID ?© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

Ethernet Operation

!"C #ubla$er



Ethernet Operation

!"C #ubla$er

%ata encapsulation7 9rame assem'ly 'efore transmission and frame disassem'ly %!on

rece!tion of a frame

7 )AC layer adds a header and trailer to the net&or- layer PD@

Provides three pri&ar$ 'unctions:7 9rame delimiting 6 identifies a gro%! of 'its that ma-e %! a frame,

synchroni ation 'et&een the transmitting and receiving nodes

7 Addressing 6 each $thernet header added in the frame contains the!hysical address :)AC address< that ena'les a frame to 'e deliveredto a destination node

7 $rror detection 1 each $thernet frame contains a trailer &ith a cyclicred%ndancy chec- :C*C< of the frame contents


11/67Presentation_ID © 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

Ethernet Operation

!"C #ubla$er

!edia "ccess Control7 *es!onsi'le for the !lacement of frames on the media and the

removal of frames from the media

7 Comm%nicates directly &ith the !hysical layer

7 If m%lti!le devices on a single medi%m attem!t to for&ard datasim%ltaneo%sly, the data &ill collide res%lting in corr%!ted, %n%sa'ledata

7 $thernet !rovides a method for controlling ho& the nodes shareaccess thro%gh the %se a Carrier Sense )%lti!le Access :CS)A<technology



Ethernet Operation

!edia "ccess Control

Carrier #ense !ultiple "ccess (C#!") process7 @sed to first detect if the media is carrying a signal

7 If no carrier signal is detected, the device transmits its data

7If t&o devices transmit at the same time 1 data collision


13/67Presentation_ID /© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

Ethernet Operation




Ethernet Operation


he t&o commonly %sed methods are#C#!"*Collision %etection

7 he device monitors the media for the !resence of a data signal

7 If a data signal is a'sent, indicating that the media is free, the devicetransmits the data

7 If signals are then detected that sho& another device &as transmittingat the same time, all devices sto! sending and try again later

7 Bhile $thernet net&or-s are designed &ith CS)A CD technology, &ith

today s intermediate devices, collisions do not occ%r and the !rocesses%tili ed 'y CS)A CD are really %nnecessary

7 Bireless connections in a A4 environment still have to ta-e collisionsinto acco%nt


15/67Presentation_ID "© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

Ethernet Operation


he t&o commonly %sed methods are#C#!"*Collision "voidance (C#!"*C") &edia access&ethod7 Device e+amines the media for the !resence of data signal 1 if the

media is free, the device sends a notification across the media of itsintent to %se it

7 he device then sends the data.

7 @sed 'y 802. &ireless net&or-ing technologies



Ethernet Operation



17/67Presentation_ID =© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

Ethernet Operation

!"C "ddress: Ethernet Identit$

7 ayer 2 $thernet )AC address is a 381'it 'inary val%e e+!ressed as 2he+adecimal digitsI$$$ re %ires a vendor to follo& t&o sim!le r%les#7 )%st %se that vendor s assigned @I as the first / 'ytes7 All )AC addresses &ith the same @I m%st 'e assigned a %ni %e

val%e in the last / 'ytes



Ethernet Operation

+ra&e Processin,

)AC addresses assigned to &or-stations, servers, !rinters, s&itches,and ro%ters$+am!le )ACs# 0010"1?A1/C1=8100, 00#0"#?A#/C#=8#00, or000".?A/C.=800.

9or&arded message to an $thernet net&or-, attaches headerinformation to the !ac-et, contains the so%rce and destination )ACaddress$ach 4IC vie&s information to see if the destination )AC address inthe frame matches the device s !hysical )AC address stored in *A)

4o match, the device discards the frame)atches the destination )AC of the frame, the 4IC !asses the frame%! the SI layers, &here the deca!s%lation !rocess ta-es !lace


19/67



Ethernet +ra&e "ttributes

Ethernet +ra&e #i-e

$thernet II and I$$$ 802./ standards define the minim%mframe si e as 53 'ytes and the ma+im%m as " 8 'ytes

ess than 53 'ytes in length is considered a EcollisionfragmentE or Er%nt frameFIf si e of a transmitted frame is less than the minim%m orgreater than the ma+im%m, the receiving device dro!s theframe

At the !hysical layer, different versions of $thernet vary intheir method for detecting and !lacing data on the media




Ethernet +ra&e #i-e

he fig%re dis!lays the fields contained in the 802. G H A4 tag




Introduction to the Ethernet +ra&e

Prea&ble and#tart +ra&e

%eli&iter +ields@sed forsynchroni ation'et&een thesending andreceiving devices

en,th* $pe+ield

Defines the e+actlength of theframe s data fielddescri'es &hich!rotocol isim!lemented

%ata andPad +ields

Contain theenca!s%lateddata from ahigher layer,an IPv3!ac-et


23/67Presentation_ID 2/© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential


Introduction to the Ethernet +ra&e

+ra&e Check #e/uence +ield

@sed to detect errors in a frame&ith cyclic red%ndancy chec- :3'ytes



Ethernet !"C

!"C "ddresses and 0e adeci&al


25/67Presentation_ID 2"© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

Ethernet !"C

!"C "ddress 2epresentations


26/67


Ethernet !"C

3nicast !"C "ddress


27/67


28/67


Ethernet !"C

!ulticast !"C "ddress

!ulticast !"C address is aspecial value that be,ins with

1 5E in he adeci&al

2an,e o' IP78 &ulticast addressesis 998. . . to 9 ;.955.955.955


29/67


30/67

Presentation_ID /0© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

Ethernet !"C

End to End Connectivit$< !"C< and IP


31/67


32/67


5.9

"ddress 2esolution Protocol


33/67

Presentation_ID //© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

"2P

Introduction to "2P

A*P P%r!oseSending node needs a &ay to find the )AC address of thedestination for a given $thernet lin-

he A*P !rotocol !rovides t&o 'asic f%nctions#

*esolving IPv3 addresses to )AC addresses

)aintaining a ta'le of ma!!ings


34/67


"2P

Introduction to "2P


35/67

Presentation_ID /"© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

"2P

"2P +unctions*Operation

A*P a'le 6@sed to find the data lin- layer address that is ma!!ed to thedestination IPv3 address

As a node receives frames from the media, it records the so%rce IPand )AC address as a ma!!ing in the A*P ta'le

A*P re %est 6ayer 2 'roadcast to all devices on the $thernet A4

he node that matches the IP address in the 'roadcast &ill re!ly

If no device res!onds to the A*P re %est, the !ac-et is dro!!ed'eca%se a frame cannot 'e created

#tatic &ap entries can be entered in an "2P table< but

this is rarel$ done


36/67


"2P



37/67


38/67


"2P



39/67

Presentation_ID /?© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

"2P



40/67


"2P



41/67


42/67


"2P

"2P 2ole in 2e&ote Co&&unication

If the destination IPv3 host is on the local net&or-, theframe &ill %se the )AC address of this device as thedestination )AC address

If the destination IPv3 host is not on the local net&or-, theso%rce %ses the A*P !rocess to determine a )AC addressfor the ro%ter interface serving as the gate&ay

In the event that the gate&ay entry is not in the ta'le, an A*P re %est is %sed to retrieve the )AC addressassociated &ith the IP address of the ro%ter interface


43/67

Presentation_ID 3/© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

"2P

2e&ovin, Entries 'ro& an "2P able

A*P cache timer removes A*P entries that have not 'een%sed for a s!ecified !eriod of time

Commands may also 'e %sed to man%ally remove all or

some of the entries in the A*P ta'le


44/67


"2P

"2P ables on Networkin, %evices


45/67

Presentation_ID 3"© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

"2P Issues

0ow "2P Can Create Proble&s


46/67


"2P Issues

!iti,atin, "2P Proble&s


48/67


#witchin,

#witch Port +unda&entals

a$er 9 "N switch

Connects end devices to a central intermediate device onmost $thernet net&or-s

Performs s&itching and filtering 'ased only on the )ACaddressJ%ilds a )AC address ta'le that it %ses to ma-e for&ardingdecisionsDe!ends on ro%ters to !ass data 'et&een IP s%'net&or-s


49/67

Presentation_ID 3?© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

#witchin,

#witch !"C "ddress able

1. he s&itch receives a 'roadcast frame from PC on Port .9. he s&itch enters the so%rce )AC address and the s&itch

!ort that received the frame into the address ta'le.. Jeca%se the destination address is a 'roadcast, the s&itch

floods the frame to all !orts, e+ce!t the !ort on &hich itreceived the frame.8. he destination device re!lies to the 'roadcast &ith a

%nicast frame addressed to PC .

Contin%edK


50/67

Presentation_ID "0© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

#witchin,

#witch !"C "ddress able

5. he s&itch enters the so%rce )AC address of PC 2 and the!ort n%m'er of the s&itch !ort that received the frame intothe address ta'le. he destination address of the frame andits associated !ort is fo%nd in the )AC address ta'le.

6. he s&itch can no& for&ard frames 'et&een so%rce anddestination devices &itho%t flooding, 'eca%se it has entriesin the address ta'le that identify the associated !orts.


52/67


#witchin,

"uto !%I=


53/67

Presentation_ID "/© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

#witchin,

+ra&e +orwardin, !ethods on Cisco #witches


54/67


#witchin,

Cut throu,h #witchin,&o variants#

+ast 'orward switchin, #7 o&est level of latency

immediately for&ards a!ac-et after reading thedestination address,ty!ical c%t1thro%ghmethod of s&itching

+ra,&ent 'ree switchin, #7 S&itch stores the first

53 'ytes of the frame'efore for&arding, mostnet&or- errors andcollisions occ%r d%ringthe first 53 'ytes


55/67

Presentation_ID ""© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

#witchin,

!e&or$ 4u''erin, on #witches


56/67


+i ed or !odular

+i ed verses !odular Con'i,uration


57/67


58/67


+i ed or !odular

!odule Options 'or Cisco #witch #lots


59/67

Presentation_ID "?© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

a$er #witchin,

a$er 9 verses a$er #witchin,


60/67


a$er #witchin,

Cisco E press +orwardin,

&o main com!onents#

9or&arding information 'ase :9IJ<7 Conce!t%ally similar to a ro%ting ta'le

7 A net&or-ing device %ses this loo-%! ta'le to ma-edestination1'ased s&itching decisions d%ring Cisco$+!ress 9or&arding o!eration

7 @!dated &hen changes occ%r in the net&or- andcontains all ro%tes -no&n at the time

Ad(acency ta'les7 )aintain layer 2 ne+t1ho! addresses for all 9IJ entrie s


61/67


a$er #witchin,

Cisco E press +orwardin,


62/67


63/67

Presentation_ID 5/© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

a$er #witchin,

Con'i,urin, a 2outed Port on a a$er #witch


64/67


Chapter 5

#u&&ar$

$thernet is the most &idely %sed A4 technology %sed today.$thernet standards define 'oth the ayer 2 !rotocols and the

ayer technologies.

he $thernet frame str%ct%re adds headers and trailers

aro%nd the ayer / PD@ to enca!s%late the message 'eingsent.

As an im!lementation of the I$$$ 802.2 / standards, the$thernet frame !rovides )AC addressing and error chec-ing.

*e!lacing h%'s &ith s&itches in the local net&or- hasred%ced the !ro'a'ility of frame collisions in half1d%!le+ lin-s.


65/67

Presentation_ID 5"© 2008 Cisco Systems, Inc. All r ights reserved. Cisco Confidential

Chapter 5

#u&&ar$

he ayer 2 addressing !rovided 'y $thernet s%!!orts%nicast, m%lticast, and 'roadcast comm%nications.

$thernet %ses the Address *esol%tion Protocol to determinethe )AC addresses of destinations and ma! them against-no&n 4et&or- layer addresses.

$ach node on an IP net&or- has 'oth a )AC address and anIP address.

he A*P !rotocol resolves IPv3 addresses to )AC

addresses and maintains a ta'le of ma!!ings. A ayer 2 s&itch '%ilds a )AC address ta'le that it %ses toma-e for&arding decisions.


66/67


Chapter 5

#u&&ar$

ayer / s&itches are also ca!a'le of !erforming ayer /ro%ting f%nctions, red%cing the need for dedicated ro%ters ona A4.

ayer / s&itches have s!eciali ed s&itching hard&are sothey can ty!ically ro%te data as %ic-ly as they can s&itch.


67/67

Documents

ITN InstructorPPT Chapter 5 Cisco