L2 & L3 mechnisme

8/10/2019 L2 & L3 mechnisme

1/21

01/18/15 IS8040 1

Layer 2 and Layer 3 SwitchingFreeha Khan

2nd PresentationIS 8040Data Co !nication "heory and Practice


2/21

01/18/15 IS8040 2

SwitchingToday in data communications, all switchingand routing equipment perform two basicoperations:

Switching data frames Maintenance of switching operationsSwitching is the process of taking an incomingframe from one interface and delivering it out

through another interfaceRouters use Layer switching to route apacket, and switches !Layer " switches# useLayer " switching to forward frames


3/21


4/21

01/18/15 IS8040 4

Switches

%&'%&&()bps *thernet Switches are goodresolution if *thernet L+ s are stretched to

the breaking point under the weight of new users, servers and high(end applications)ost switches provide shared or dedicated%&'%&& uplinks to other switches or networkbackbones, and some even provide one ortwo dedicated -igabit *thernet links forespecially heavy bandwidth requirements


5/21

01/18/15 IS8040 5

Layer 2 Switching

Layer " switches,operate at the

second, or data link,layer of the opensystemsinterconnection

model

OSI Model

#$$%ication

PresentationSession"rans$ort

&etwor'Data Lin'Physica%


6/21

01/18/15 IS8040 (

Layer 2 Switch

-arrett .ommunications )agnum switchescome with eight to "/ %&'%&&()bps ports andrange in price from 0122 to 0%,%223


7/21


8/21


9/21


10/21

01/18/15 IS8040 10

Layer 2 Switching

I, the Layer 2 switch does not 'now where tosend the ,ra e it +roadcasts the ,ra e o!t a%% its$orts to the networ' to %earn the correctdestination

hen the ,ra e s re$%y is ret!rned the switch

%earns the %ocation o, the new address and addsthe in,or ation to the switching ta+%e


11/21

01/18/15 IS8040 11

Layer 3 Switching

Layer switchingoperates at the

network layer

SI *ode%#$$%ication

PresentationSession"rans$ort

&etwor'Data Lin'Physica%


12/21

01/18/15 IS8040 12

Layer 3 Switch

Li ited $!r$ose

Layer 3 switches are on%y a.ai%a+%e ,orthernet"hey on%y ro!te IP/IP6 $rotoco%s

Ca$a+%e to $er,or ro!ting at wires$eed7 10 100 1000 *+$s


13/21

01/18/15 IS8040 13

Layer 3 Switching

ardware +ased $ac'et to $ac'et IPro!ting- ardware +ased ro!ters cost %ess than

traditiona% so,tware +ased ro!ters

"hey switch non ro!ta+%e tra,,ic to Layer 2


14/21

01/18/15 IS8040 14

Layer 3 Switch

Rapier T) %&'%&& Layer Switch


15/21

01/18/15 IS8040 15

Layer 3 Switching

7t e$amines packet information andforwards packets based on theirnetwork(layer destination addressesLayer switching also supportsrouter functionality


16/21

01/18/15 IS8040 1(

Layer 3 Switching

Flow of intersubnet traffic with Layer 3 switches


17/21

01/18/15 IS8040 1)

Di,,erence +etween Layer 2 and

Layer 3 Switches"he di,,erence +etween Layer 2 and Layer 3switching is the ty$e o, in,or ation inside the

,ra e that is !sed to deter ine the correcto!t$!t inter,aceith Layer 2 switching ,ra es are switched

+ased on *#C address in,or ationith Layer 3 switching ,ra es are switched

+ased on networ' %ayer in,or ation


18/21

01/18/15 IS8040 18


Layer 3 SwitchesLayer " switching does not lookinside a packet for network(layerinformation as does layer switchingLayer " switching is performed bylooking at a destination )+.address within a frame


19/21

01/18/15 IS8040 1


Layer 3 SwitchesLayer switches looks at the frame8sdestination address and sends it to the

appropriate interface if it knows thedestination address locationLayer " switching builds and maintains a

switching table that keeps track of which)+. addresses belong to each port orinterface


20/21

01/18/15 IS8040 20

9e,erences

Switched, Fast, and Gigabit Ethernet 9o+ert:reyer and Sean 9i%ey "hird dition

Business Data Communications Sta%%ingsFo!rth ditionhtt$7//www;gcn;cohtt$7//www;s%ac;stan,ord;ed!/htt$7//www;cisco;co /!ni.ercd


21/21

01/18/15 IS8040 21

9e,erences

htt$7//www;gcn;co /state/.o%(

Documents

L2 & L3 mechnisme