Giao thức định tuyến - Chapter 7 pdf

RIPv2
Routing Protocols and Concepts – Chapter 7
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
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Objectives
 En
cou
nt
e
r
a
n
d

desc
ri
be
th
e
limit
a
ti
o
n
s

o
f RIPv1’
s

cou e a d desc be e a o s o s
limitations.

Apply the basic Routing Information Protocol Version
Apply

the

basic

Routing

Information

Protocol

Version

2 (RIPv2) configuration commands and evaluate
RIPv2 classless routing updates.
 Analyze router output to see RIPv2 support for VLSM
and CIDR
 Identify RIPv2 verification commands and common
RIPv2 issues.
 Configure, verify, and troubleshoot RIPv2 in “hands-
on” labs
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Introduction
Introduction
 Difference between RIPv1 & RIPv2

RIPv1

RIPv1
•A classful distance vector routing protocol
•
Does not support discontiguous subnets
Does

not

support

discontiguous

subnets
•Does not support VLSM
•Does not send subnet mask in routing update
•Routing updates are broadcast
RIPv2
•A classless distance vector routing protocol that is an
enhancement of RIPv1
’
s features
enhancement

of

RIPv1 s

features
.
•Next hop address is included in updates
•Routing updates are multicast (224.0.0.9 vs. 255.255.255.255)
/>d/doc/cisintwk/ito_doc/rip.htm
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•The use of authentication is an option
Introduction
 Similarities between RIPv1 & RIPv2
–
Use of timers to prevent routing loops
Use

of

timers

to

prevent

routing

loops
– Use of split horizon or split horizon with poison reverse to
also help prevent routing loops.
– Use of triggered updates when there is a change in the
topology for faster convergence.
Maximum hop count of 15 with the hop count of 16 signifying
–
Maximum

hop

count

of

15
,
with

the

hop

count

of

16

signifying

an unreachable network.
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RIP 1 Li it ti
RIP
v
1

Li
m
it
a
ti
ons
 Lab Topology
3t t

3
rou
t
er se
t
up
Topology is discontiguous
There exists a static summary route
Static route information can be
injected into routing table updates

using redistribution.

Routers 1 & 3 contain VLSM
Routers

1

&

3

contain

VLSM

networks
Remember that both the R1 and R3
routers have subnets that are part of
the 172 30 0 0/16 major classful
the

172
.
30
.
0
.
0/16

major

classful

network (class B).
Also remember that R1 and R3 are
connected to R2 usin
g
subnets of the
g
209.165.200.0/24 major classful
network (class C).
This topology is discontiguous and
will not converge because
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will

not

converge

because

172.30.0.0/16 is divided by the
209.165.200.0/24.
RIP 1 Li it ti
RIP
v

1

Li
m
it
a
ti
ons
 The topology shows that
R2 has a static
R2

has

a

static

summary route to the
192.168.0.0/16 network.
The configuration of this
summar
y
route will be
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y
displayed later in this

section.
RIP 1 Li it ti
RIP
v
1

Li
m
it
a
ti
ons
 Review the VLSM addressing
scheme in the figure As shown
scheme

in

the

figure
.
As

shown

in the top chart, both R1 and R3
have had the 172.30.0.0/16
network subnetted into /24
subnets

subnets
.
–Four of these /24 subnets are
assigned:
–
two to R1
(
172.30.1.0/24 and
(
172.30.2.0/24)
–two to R3 (172.30.100.0/24 and
172.30.110.0/24).
Ithbtt ht h

I
n
th
e
b
o
tt
om c
h
ar
t
, we
h
ave
taken the 172.30.200.0/24
subnet and subnetted it again,

usin
g
the first four bits for
g
subnets and the last four bits for
hosts. The result is a
255.255.255.240 mask or /28.
Subnet 1 and Subnet 2 are
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Subnet

1

and

Subnet

2

are

assigned to R3.
RIP 1 Limitations
RIP
v
1

Limitations
 Scenario Continued
S
 VL
S
M
-Recall this is sub netting the
subnet
 Private IP addresses are on
LAN links
 Public IP addresses are used
on WAN links (through an
ISP, or when inside users
dt t id it
nee
d

t
o access ou
t
s
id
e s
it
es,
a public IP address must be
used.)
 Loopback interfaces
-These are virtual interfaces
that can be pinged and

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that

can

be

pinged

and

added to routing table
Cisco has set these addresses aside for educational purposes.
RIPv1 Limitations
 Loopback interfaces
Notice that R3 is using loopback interfaces (Lo0,
Lo1, and Lo2).
A loopback interface is a software-only interface that
is used to emulate a physical interface
is

used

to

emulate

a

physical

interface
.
Like other interfaces, it can be assigned an IP address.
Loopback interfaces are also used by other routing
p
rotocols
,
such as OSPF
,
for different
p
ur
p
oses.
p, , pp
These uses will be discussed in Chapter 11 OSPF.
In a lab environment, loopback interfaces are useful
in creating additional networks without having to add
more physical interfaces on the router
more

physical

interfaces

on

the

router
.
A loopback interface can be pinged and the subnet
can be advertised in routing updates.

Therefore, loopback interfaces are ideal for
Therefore,

loopback

interfaces

are

ideal

for

simulating multiple networks attached to the same
router.
In our example, R3 does not need four LAN
interfaces to demonstrate multiple subnets and
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interfaces

to

demonstrate

multiple

subnets

and

VLSM. Instead, we use loopback interfaces.
RIPv1 Limitations
RIPv1

Limitations
 Route redistribution
Redistribution involves taking the routes from one routing
–
Redistribution

involves

taking

the

routes

from

one

routing

source and sending those routes to another routing source.
• In our example topology, we want the RIP process on R2 to
redistribute our static route (192.168.0.0/16) by importing the route
into RIP and then sending it to R1 and R3 using the RIP process.
R2( fi
t)#ditibt tti
-
R2(
con
fi
g-rou
t
er
)#
re
di
s
t
r
ib
u
t
e s
t
a

ti
c
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RIPv1 Limitations
RIPv1

Limitations
 R2(config)#ip route 192.168.0.0 255.255.0.0 Null0
The address space represented by the static summary route
–
The

address

space

represented

by

the

static

summary

route

192.168.0.0/16 does not actually exist.
–In order to simulate this static route, we use a null interface as
the exit interface.
– You do not need to enter any commands to create or
configure the null interface
configure

the

null

interface
.
–It is always up but does not forward or receive traffic. Traffic
sent to the null interface is discarded.
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Static routes and null interfaces

Stat
i
c
r
outes

a
n

d
n
u
ll in
te
rf
aces
Stat c outes a d u te aces
R2(config)#ip route 192.168.0.0 255.255.0.0 Null0

a static route must have an active exit interface
a

static

route

must

have

an

active

exit

interface

before it will be installed in the routing table.

Usin
g
the null interface will allow R2 to advertise the
g
static route in RIP even though networks belonging
to the summary 192.168.0.0/16 do not actually exist.
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Vifi dTti C tiit
V
er
if
y
i
ng an
d

T
es
ti
ng
C
onnec
ti
v
it
y
 show ip interfaces brief

Tt thth ttht l h fll
–
T
o
t
es
t
w
h
e
th
er or no
t

th
e
t
opo
l
ogy
h
as
f
u
ll

connectivity, we first verify that both serial
links on R2 are up using the show ip
interface brief
 Ping

Whenever R2 pings any of the 172.30.0.0 subnets
on R1 or R3, only about 50% of the ICMP are
successful.
R1 is able to ping 10.1.0.1 but is unsuccessful
when attempting to ping the 172.30.100.1 on R3

R3 is able to ping 10 1 0 1 but is unsuccessful

R3

is

able

to

ping

10
.
1
.
0
.
1

but

is

unsuccessful

when attempting to ping the 172.30.1.1 on R1.
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RIP 1 Li it ti
RIP
v
1

Li
m
it
a
ti
ons
 RIPv1 – a classful routing protocol
–
Subnet mask
are not sent
in updates
Subnet

mask

are

not

sent
in

updates
–Summarizes networks at major network boundaries
–RIPv1 cannot support discontiguous networks, VLSM, or CIDR.
if t k i di ti d RIP 1 fi d ill t b
–
if
ne
t
wor
k

i
s
di
scon
ti
guous an
d

RIP
v
1
con
fi
gure
d

convergence w
ill
no
t

b
e
reached
–RIPv1 on both the R1 and R3 routers will summarize their 172.30.0.0
subnets to the classful major network address of 172 30 0 0 when sending
subnets

to

the

classful

major

network

address

of

172
.
30
.

0
.
0

when

sending

routing updates to R2.
–From the perspective of R2, both updates have an equal cost of 1 hop to
reach network 172 30 0 0/16
As you will see R2 installs both paths in the
reach

network

172
.
30
.
0
.
0/16
.
As

you

will

see
,
R2

installs

both

paths

in

the

routing table.
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RIP 1 Li it ti
RIP
v
1

Li
m
it
a
ti
ons

Examining the routing tables
-To examine the contents of
routing updates use the
debug ip rip command
R2 i i i t 172 30 0 0 l t
R2

i
s rece
i
v
i
ng
t
wo
172
.
30
.
0
.
0
equa
l
cos
t

routes with a metric of 1 hop. R2 is
receiving one route on Serial 0/0/0 from R1
and the other route on Serial 0/0/1 from R3.

R2 has two equal cost routes to the
172.30.0.0/16 network.
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RIP 1 Li it ti
RIP
v
1

Li
m
it
a
ti
ons
•
R1 has its own 172 30 0 0 routes:
•
R1

has

its

own

172
.

30
.
0
.
0

routes:

172.30.2.0/24 and 172.30.1.0/24.
•But R1 does not send R2 those subnets.
•R3 has a similar routing table.
BthR1 dR3 b d t d
•
B
o
th

R1
an
d

R3
are
b
oun
d
ary rou
t
ers an
d

are only sending the summarized
172.30.0.0 network to R2 in their RIPv1
routing updates.
AltR2lkbtth
•R2 that it is not including the 172.30.0.0 network
in its updates to either R1 or R3.
•Because the split horizon rule is in effect
.
•
R2 learned about 172 30 0 0/16 on both the
•
A
s a resu
lt
,
R2
on
l
y
k
nows a
b
ou
t

th
e
172.30.0.0/16 classful network and is
unaware of any 172.30.0.0 subnets.

•
R2

learned

about

172
.
30
.
0
.
0/16

on

both

the

Serial 0/0/0 and Serial 0/0/1 interfaces, it does not
include that network in updates it sends out these
same interfaces.
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RIPv1 Limitations
RIPv1

Limitations
 Because RIPv1 does not send the
subnet mask in routin
g
u
p
dates, it
R4 is added to
gp
cannot support VLSM.
 R3 router is configured with VLSM
subnets all of which are members
R4

is

added

to

the topology
connected to R3
subnets
,
all

of

which

are

members

of the class B network
172.30.0.0/16:
–
172.30.100.0/24 (FastEthernet 0/0)
172.30.100.0/24

(FastEthernet

0/0)
–172.30.110.0/24 (Loopback 0)
–172.30.200.16/28 (Loopback 1)
172 30 200 32/28 (L b k 2)
–
172
.
30
.
200
.
32/28

(L
oop
b
ac

k

2)
 As we saw with the 172.30.0.0/16
u
p
dates to R2 b
y
R3,
py
–RIPv1 either summarizes the
subnets to the classful boundary
–
or
uses

t
h
e

sub
n
et
m
as
k
o
f
t
h

e

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o
uses t e sub et as o t e
outgoing interface to determine
which subnets to advertise.
RIPv1 Limitations
RIPv1

Limitations
 Why is RIPv1 on R3 not including
the other subnets,
172 30 200 16/28 and
R4 is added to
172
.
30
.
200
.
16/28

and

172.30.200.32/28, in updates to
R4?

–
Those subnets do not have the
R4

is

added

to

the topology
connected to R3
Those

subnets

do

not

have

the

same subnet mask as
FastEthernet 0/0.
– R3 will only include those
172 30 0 0 routes in its routing
172
.

30
.
0
.
0

routes

in

its

routing

table with the same mask as the
exit interface.
– Since the interface is 172.30.100.1
ith /24 k it ill l i l d
w
ith
a
/24
mas
k
,
it
w
ill
on
l

y
i
nc
l
u
d
e
172.30.0.0 subnets with a /24
mask. The only one that meets
this condition is 172.30.110.0.
– The other 172.30.0.0 subnets,
172.30.200.16/28 and
172.30.200.32/28, are not
included because the /28 masks
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do not match the /24 mask of the
outgoing interface.
RIP 1 Li it ti
RIP
v
1

Li
m
it
a
ti

ons
 No CIDR Support
R2(config)#ip route 192 168 0 0
R2(config)#ip

route

192
.
168
.
0
.
0

255.255.0.0 Null0
–the static route is included in
R2's routing table, but R2 will
not include the static route in its
not

include

the

static

route

in

its

update
–R1 is not receiving this
192.168.0.0/16 route in its RIP
updates from R2,
 Reason: Classful routing
p
rotocols do not su
pp
ort
p
pp
CIDR routes that are
summarized with a smaller
mask than the classful
bt k
su
b
ne
t
mas
k
–If the 192.168.0.0 static route
were configured with a /24 mask
or
g
reater
,

this route would be
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g,
included in the RIP updates.
Config ring RIP 2
Config
u
ring

RIP
v
2
 Comparing RIPv1 & RIPv2 Message Formats
–
RIPv2 Messa
g
e format is simila
r
to RIPv1 but has 2 extensions
g
1st extension is the subnet mask field
allows a 32 bit mask to be included in the RIP route entry.

the receiving router no longer depends upon the subnet mask of the
the

receiving

router

no

longer

depends

upon

the

subnet

mask

of

the

inbound interface or the classful mask when determining the subnet
mask for a route
2nd extension is the addition of next hop address
The Next Hop address is used to identify a better next-hop address - if
one exists - than the address of the sending router.
If the field is set to all zeros (0.0.0.0), the address of the sending router
is the best next
-
hop address

is

the

best

next
-
hop

address
.
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Configuring RIPv2

Enabling and Verifying RIPv2

Enabling

and

Verifying

RIPv2
 Configuring RIP on a Cisco router
–
By default it is running RIPv1

–Even though the router only sends RIPv1 messages, it can
interpret both RIPv1 and RIPv2 messages
interpret

both

RIPv1

and

RIPv2

messages
.
–A RIPv1 router will just ignore the RIPv2 fields in the route
entry.
RIPv1
RIPv2
RIPv1
RIPv2
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Configuring RIPv2
Configuring

RIPv2

Configuring

RIPv2
on a
Configuring

RIPv2
on

a

Cisco router
-
Requires using the
-
Requires

using

the

version 2 command
RIPv2 ignores RIPv1
-
RIPv2

ignores

RIPv1

updates


To verify RIPv2 is

To

verify

RIPv2

is

configured use the
show ip protocols
show

ip

protocols
command
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Comparing RIP v1 and v2
Comparing

RIP

v1

and

v2
 RIP v2 Æ send and receive v2

RIP v1
Æ
send v1 but can receive both v1 and v2
RIP

v1

Æ
send

v1

but

can

receive

both

v1

and

v2
No I can not

Ild
RIP network is broken
Version 1
Version 2
No
.
I

can

not

take version 1
I
can on
l
y sen
d

version 1
Version

1
Version

2
Yes. I can take
version 1 or 2
I can only send
version 2

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POP Quiz
POP

Quiz
 How do you make the RIPv2 back to the default “send 1” and
receive 1 or 2”?
- Hint: Gad(config-router)#version 1 is not the answer.
Version 1
Version 2
Version

1
Version

2
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Cfi i RIP2
C
on
fi
gur
i
ng

RIP
v
2

Auto
-
Summary & RIPv2
Auto
Summary

&

RIPv2
 RIPv2 will automatically
summarize routes at major
summarize

routes

at

major

network boundaries and
can also summarize routes
with a subnet mask that is
smaller than the classful
subnet mask
subnet

mask
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