routing network layer (computer networking)
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Chapter 4Network Layer
ComputerNetworking: ATop Down
Approach
6th
edition Jim Kurose, KeithRossAddison-WesleyMarh !"#!
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Network Layer 4-#
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Network Layer 4-!
Routin$
chapter goals: understand priniples %ehind network
layer ser&ies'
network layer ser&ie models (orwardin$ &ersus routin$ how a router works routin$ )path seletion*
%roadast, multiast instantiation, implementation in the
+nternet
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+ts a Matter o( rotool
.o %uild %i$ networks, you need to use routers andthey ha&e to talk to eah other/
Routers need to e0han$e routes with eah other/
.hey use &arious routin$ protools to e0han$eroutes/
+n today disussion, you will 1rst see how tomanually enter a route, then you will learn how to
implement the simple R+ routin$ protool/
2inally you will learn how to setup 3+R )+nteriorateway Routin$ rotool )Ciso proprietary**, anad&aned routin$ protool/
Network Layer 4-5
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30ample
Network Layer 4-4
o how do we get
routers to communicate
with
each other when they’re
not directly connected?
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Network Layer 4-
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Network Layer 4-6
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Routin$ .a%les
Routin$ ta%les tell routers where to send pakets/
.wo routers an automatially route paketswhen they share a ommon + network spae8
network address/
9ut what a%out when routers arent onnetedto eah other diretly:
.hey need to know how to send pakets to the otherrouter/
.hey $et this in(ormation (rom routing tables,ta%les whih are stored in the memory of therouter/
Network Layer 4-;
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Routin$ .a%les
+n Ciso Router, we used show ip route ommandto show the routin$ ta%le/
Network Layer 4-<
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Routin$ .a%les
.he route ta%le is a type o( address %ook (or therouter/ +t looks at a pakets destination +address, then looks that up in its routin$ ta%le/9ased on that lookup, it sends the paket to the
ri$ht plae/
3ah line in the routin$ ta%le has two parts/ .he1rst part is a letter whih tells how the route wasesta%lished/
.he seond part tells the router how to $et tothe route/ .he route ta%le is onstantly kept up-to-date %ythe router so it knows where to send pakets/
Network Layer 4-#"
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Routin$ .a%les
Network Layer 4-##
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Routin$ .a%les
Network Layer 4-#!
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Manually enter Routes
Network Layer 4-#5
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30erise
Network Layer 4-#4
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Network Layer 4-#6
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Network Layer 4-#7
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.rou%leshootin$
Network Layer 4-#;
=ow do we trou%leshoot routes i( thedata isnt $ettin$ throu$h: .he pin$ ommand tells you i( the network
and host are reaha%le/
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.rou%leshootin$
Network Layer 4-#<
>o how does the pin$ ommand work:
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.ro%leshootin$
Network Layer 4-!"
?sin$ .raeroute
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Network Layer 4-!#
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.ro%leshootin$
Static routes don’t changeautomatically. .his means that i( you ha&e stati routes
in your routin$ ta%le, you need to han$ethem manually
When there are han$es to routes, you
ha&e to modi(y those routes in yourrouters route ta%le to keep it urrent/
Network Layer 4-!!
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Network Layer 4-!5
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Network Layer 4-!4
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Network Layer 4-!
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Routin$ +n(ormationrotoolUse RIP to get routes to updatethemselves
+( you want to make your li(e easy, in&est some
time in $ettin$ a dynami routin$ protoolrunnin$ on your network/R+, or Routin$ +n(ormation rotool, is onesuh dynami routin$ protool/R+ is a way (or routers to share networkaddresses/Routers use R+ to talk to eah other, sharin$their route in(ormation and allowin$ them tokeep their route ta%les up-to-date
Network Layer 4-!6
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Network Layer 4-!7
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Network Layer 4-!;
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Network Layer 4-!<
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Network Layer 4-5"
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Routin$ +n(ormationrotoolUse RIP to get routes to updatethemselves
+( you want to make your li(e easy, in&est some
time in $ettin$ a dynami routin$ protoolrunnin$ on your network/R+, or Routin$ +n(ormation rotool, is onesuh dynami routin$ protool/R+ is a way (or routers to share networkaddresses/Routers use R+ to talk to eah other, sharin$their route in(ormation and allowin$ them tokeep their route ta%les up-to-date
Network Layer 4-5#
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Network Layer 4-5!
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Network Layer 4-55
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Network Layer 4-54
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Network Layer 4-5
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Network Layer 4-56
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Network Layer 4-57
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Network Layer 4-5;
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Network Layer 4-5<
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Network Layer 4-4"
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Network Layer 4-4#
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=ow we set up R+:
Setting up RIP on a router is reallysimple. You enter the cong mode onthe router, then e enter the routerrip conguration
Network Layer 4-4!
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Network Layer 4-45
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Network Layer 4-44
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.rou%leshootin$
Network Layer 4-4
@utput o( .rae route ommand
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.rou%leshootin$
Network Layer 4-46
i&en a hoie, the R+ protool alwayshooses the route ith the feestnumber of routers in its path, or thefeest number of !hops."
?n(ortunately, the ma#imum numberof hop$counts that the RIP protocolallos is %&.
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.rou%leshootin$
Network Layer 4-47
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.rou%leshootin$
Network Layer 4-4;
R+ an only use the hop ount to 1ndthe %est route/
R+ doesnt know the speed o( apartiular network line, so it treats alllines eually/ .his means that i( there are two possi%le
routes to a partiular network, RIP ill
choose the one ith the loest hopcount, e&en i( the other route is really (ast/
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.rou%leshootin$
Network Layer 4-4<
R+ doesnt know the speed o( apartiular network line, so it treats alllines eually/ .his means that i( there are two possi%le
routes to a partiular network, RIP illchoose the one ith the loest hopcount, e&en i( the other route is really (ast/
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Network Layer 4-"
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Network Layer 4-#
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Network Layer 4-!
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Network Layer 4-5
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Network Layer 4-4
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