routing network layer (computer networking)

8/18/2019 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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routing network layer (computer networking)

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