Semester 3 Semester 3 Semester 3 Semester 3

needleorderΔίκτυα και Επικοινωνίες

24 Οκτ 2013 (πριν από 3 χρόνια και 11 μήνες)

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Semester 3Semester 3
Semester 3Semester 3
CHAPTER 1CHAPTER 1
Secció de Telemàtica
Secció de Telemàtica
Content
Content

VLSM

VLSM
•RIPv2
VLSMVLSM
VLSMVLSM
VLSM
VLSM

V
LSM Variable Lenght Subnet Masks
•Way to use address space more efficiently Use
lktkithfhtd
a
l
ong mas
k
on ne
t
wor
k
s w
ith

f
ew
h
os
t
s, an
d
a
short mask on subnets with many hosts
WorkswithCiscoroutersandOSPFRIPv2

Works

with

Cisco

routers

and

OSPF
,
RIPv2
,
EIGRP, IS-IS, Static routing Classless Routing
p
rotocol
p
–They announce the address and the mask in the updates
•VLSM allows an or
g
anization to use more than
g
one subnet mask within the same network address
space Subnetting a subnet
Calculating VLSM
Calculating VLSM
VLSM Example: Subnetting
VLSM Example: Subnetting
•Class C Address subnetted with 3 bits

8subnets/27
8

subnets

/27
•Waste of space for point to point links 
Onlyneed2hostspersubnet!!
Only

need

2

hosts

per

subnet

!!
VLSM Example: Point to point links
VLSM Example: Point to point links
BkClC

B
rea
k

Cl
ass
C

into subnets
fibl
o
f
var
i
a
bl
e
lenght
•One subnet is
break in more
sub-subnets

/30subnets
/30

subnets

only permit
two hosts
VLSM Example: Final design
VLSM Example: Final design
•For point to point links /30 subnets
FLAN

Rﱬ

F
or
LAN
s

R


イ

」

﹧




Subnet Zero
Subnet Zero
•It has become acce
p
table
p
ractice to
pp
use the first and last subnets in a
subnettednetworkinconjunction
subnetted

network

in

conjunction

with VLSM.
–Router# ip subnet-zero

BydefaultfromIOS120

By

default

from

IOS

12
.
0
Route summarization
Route summarization

AggregationorSummarization

Supernetting

Aggregation

or

Summarization


Supernetting
–Notice a group of networks in one supernetwork by
l
oo
kin
g
f
o
r
co
mm
o
n
b
i
ts
fr
o
m
t
h
e
l
e
f
t
oogocoobtsoteet
•Try to keep the subnetwork numbers grouped
togetherinthenetworktoallowforaggregation
together

in

the

network

to

allow

for

aggregation
Route summarization example
Route summarization example
•Only possible if the routers of a network
runaclasslessroutingprotocolsuchas
run

a

classless

routing

protocol
,
such

as

OSPF or EIGRP
•Reduce the size of routing tables
RIP2RIP2
RIP
v
2RIP
v
2
RIP History
RIP History
•RIP IGP protocol designed for moderate AS
RIP1

RIP
v
1

–Classfull routing protocol
–Vector distance protocol that broadcasts its entire
routing table to each neighbor router
–30 seconds by default and 15 number of hops
Loadbalancingover6equal
costpaths(4by

Load

balancing

over

6

equal
-
cost

paths

(4

by

default)
RIPv1 Config. And limitations
RIPv1 Config. And limitations
•RIPv1 confi
g
uration is sim
p
le
gp
Router(config)# router rip
Router(config
-
router)#network
Router(config
router)#

network

<address>
•RIPv1 Limitations
–It does not send subnet mask information in
its updates.
–It sends updates as broadcasts on
255.255.255.255.
Itdoesnotsupportauthentication

It

does

not

support

authentication
.
–It is not able to support VLSM or classless
interdomainrouting(CIDR).
interdomain

routing

(CIDR).

RIPv2
RIPv2
•It is a distance vector
p
rotocol that uses a ho
p

pp
count metric.
•It uses holddown timers to
p
revent routin
g
loo
p
s
pgp
default is 180 seconds.
•It uses split horizon to prevent routing loops.
•It uses 16 hops as a metric for infinite distance
•Provides
p
refix routin
g
Subnet mask
pg
information in the update
•Compatible with VLSM
•Provides authentication on its updates

Multicastroutingupdates


ﵵﱴ北

葉





RIPv1 vs. RIPv2
RIPv1 vs. RIPv2
Configuring RIPv2
Configuring RIPv2
Verifying RIPv2
Verifying RIPv2
•Show ip protocols Displays values
aboutroutingprotocolsandrouting
about

routing

protocols

and

routing

protocol timer information associated
with the route
r

Showiproute

縷ﱥ

Show

ip

route


IP

route

table
•Show i
p
interface brief Summar
y
of
p
y
the information and status of an interface
Verifying RIPv2: sh ip protocols
Verifying RIPv2: sh ip protocols
Verifying RIPv2: sh ip route
Verifying RIPv2: sh ip route
Troubleshooting RIPv2
Troubleshooting RIPv2
•Display RIP routing updates as they are
sentandreceived
sent

and

received

Default Routes
Default Routes
•3 ways to learn path to destination
•Static route The system administrator manually
defines the static routes as the next hop to a
dtiti
d
es
ti
na
ti
on
–Router(config)# ip route <Dest Add> <Mask
D
est
> <N
e
x
t
H
op
>
estetop
•Default routes Path to take when there is no
known route to the destinationdefined b
y
the
y
administrator
–Router(config)# ip default-network <Next Hop>
–Router(config)# ip route 0.0.0.0 0.0.0.0
<Next Hop>

Dynamicrouting

RIPIGRPEIGRPOSPF

Dynamic

routing


RIP
,
IGRP
,
EIGRP
,
OSPF

Configuring default route
Configuring default route
•Router(config)# ip default-network
192.168.20.0 HK 2, 3, 4
Rt(fi)#it0000

R
ou
t
er
(
con
fi
g
)#

i
p rou
t
e
0
.
0
.
0
.
0

0.0.0.0 192.168.20.2 HK 1
Summary
Summary
•VLSM and the reasons for its use
•Subnetting networks of different sizes using VLSM

Routeaggregationandsummarizationastheyrelate
Route

aggregation

and

summarization

as

they

relate

to VLSM
•Router confi
g
uration usin
g
VLSM
gg
•Key features of RIP v1 and RIP v2

ImportantdifferencesbetweenRIPv1andRIPv2
Important

differences

between

RIP

v1

and

RIP

v2

•Configuration of RIP v2
VerifyingandtroubleshootingRIPv2operation

Verifying

and

troubleshooting

RIP

v2

operation

•Configuring default routes using the ip route and ip
default
networkcommands
default
-
network

commands