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Module 1WANs and
Routers
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WANS
WAN operates at the physical layer and the data
link layer of the OSI reference model.
Provide connectivity over a large geographic area
Use regional Bell companies Serial connections
Userouters, switches, modems(SU!"SU#,
communication servers(dial$in, dial$out#
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Routers & PCs
A router is a special type of computer.
It has the same basic components as a standarddesktop PC.
It has a CPU memory a system bus and !ariousinput"output interfaces.
#outers connect and allo$ communicationbet$een t$o net$orks and determine the best
path for data to tra!el throu%h the connectednet$orks.
#outers need the Internet$ork Operatin% System&IOS' soft$are to run con(%uration (les.
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Router Internal Components
)he main internal components of the router arerandom*access memory A+' non!olatilerandom*access memory &N,#A+' -ash memory
read*only memory O+' and interfaces.
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Router Internal Components
RA% is used &or
routing ta'le
in&ormation and it
holds the running
con&iguration
N)RA% is used to
store the'ac*up!startup
con&iguration &ile +lash memory is
used &or storage o&
&ull isco -S
so&tware images
R-% is used &or
permanently
storing startup
diagnostic code
.he console port
provides physicalaccess &or initial
con&iguration
.he inter&aces
provide /AN andWAN connectivity
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Routers
#outers are mainly used as WAN de!ices.
#outers use WAN connections to communicate $itheach other.
#outers are the backbone de!ices of lar%eintranets and of the Internet.
)hey operate at ayer / of the OSI model makin%decisions based on net$ork addresses.
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Functions of a Router
)he t$o main functions of a router are to select thebest path for packets and to route packets to theproper interface.
#outers build routin% tables and e0chan%e net$orkinformation $ith other routers.
Routers segment local area networ*s
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Functions of a Router Initiated !
Router Confi"uration Files
Selection o& B0S. PA.1 &or data
ontrolling the &low o& tra&&ic in and out o& the router
(switching pac*ets to appropriate inter&ace#
Speci&ying the correct set up and use o& routed and routing
protocols
Routers do this 'y 'uilding a routin" taleand sharing thatin&ormation with other routers
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An Internet#or$
A correctly con(%ured internet$ork pro!ides thefollo$in%1
2 Consistent end*to*end addressin%
2Addresses that represent net$ork topolo%ies
2 3est path selection
2 4ynamic or static routin%
2 S$itchin%
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WAN %ata in$ Protocols
)he primary functions of a WAN operate at thephysical layer and at the data link layer.
)he WAN physical layer describes the interfacebet$een the data terminal e5uipment &4)6' and the
data circuit*terminatin% e5uipment &4C6'.WAN data link protocols include the follo$in%1
2 7i%h*le!el data link control &74C'
2 8rame #elay
2 Point*to*Point Protocol &PPP'
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Academ! Approac' to WANs
In the academy lab all the net$orks $ill beconnected $ith serial or 6thernet cables.
In the real $orld serial cables are not connectedback to back.
In a real $orld situation one router could be in Ne$9ork $hile another router could be in SydneyAustralia.
In the academy lab de!ices that make up the WAN
cloud are simulated by the connection bet$een theback*to*back 4)6*4C6 cables.
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WAN Connections
We use
Academ! trainin"
simulates t'is
%() to %C)
connection
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Connectin" WAN interfaces
A WAN uses many di:erent technolo%ies to makedata connections across a broad %eo%raphic area.
WAN communication ser!ices are usually leasedfrom ser!ice pro!iders.
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Router Interfaces
AN interfaces allo# routers to connect to t'e
AN media. ('is is usuall! some form of )t'ernet.
WANs pro*ide connections t'rou"' a ser*ice
pro*ider to a distant site or to t'e Internet.
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Router Mana"ement Ports
Console
2 +sed for initial confi"uration
2 (roules'ootin"
2%eu""in"2 Monitorin" t'e s!stem
2 %ispla!s startup and error messa"es ! default,console onl!-
2 %o not depend on net#or$ connections
2 Actuall! as!nc'ronous serial ports
Auiliar! ,A+/-
2 Auiliar! for dial0in access
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Initial Connection to t'e Router
A rollo*er cale #it' a %02 to R045 adapter
Connect to t'e console port of t'e router
Connect to to t'e C6M port of a PC #it' terminal
emulation soft#are suc' as 7!per(erminal
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Confi"urin" 7!per(erminal
Confgure terminal emulation sotware onthe PC or the ollowing:
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