Giao thức định tuyến - Chapter 5 pot

RIP version 1
Routing Protocols and Concepts – Chapter 5
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
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Objectives
 D
esc
ri
be
th
e
f
u
n
c
ti
o
n
s,

c
h
a
r
ac
t
e
ri
s

ti
cs,

a
n
d

ope
r
a
ti
o
n
escbe eucos,caacescs,adopeao
of the RIPv1 protocol.

Configure a device for using RIPv1.
Configure

a

device

for

using

RIPv1.
 Verify proper RIPv1 operation.
f

 Describe how RIPv1 per
f
orms automatic
summarization.
 Configure, verify, and troubleshoot default routes
propagated in a routed network implementing RIPv1.
 Use recommended techniques to solve problems
related to RIPv1
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RIP Historical Impact
 RIP evolved from an earlier
p
rotocol
p
developed at Xerox, called Gateway
Information Protocol (GWINFO).
 With the development of Xerox Network
System (XNS) GWINFO evolved into
System

(XNS)
,
GWINFO

evolved

into

RIP.
 It later gained popularity because it was
im
p
lemented in the Berkele
y
Software
py
Distribution (BSD) as a daemon named
routed (pronounced "route-dee", not
"rout-ed").

Recognizing the need for standardization

Recognizing

the

need

for

standardization

of the protocol, Charles Hedrick wrote
RFC 1058 in 1988, in which he
documented the existing protocol and
specified some improvements
specified

some

improvements
.
 Since then, RIP has been improved with
RIPv2 in 1994 and with RIPng in 1997.
IPv6 form of RIP called
RIPng (next generation) is
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RIPng

(next

generation)

is

now available
RIPv1
 RIP Characteristics
–A classful, Distance Vector
(DV) routing protocol
(DV)

routing

protocol
–Metric = hop count
–
Routes with a ho
p
count > 15
p
are unreachable
–Updates are broadcast every
30 seconds
30

seconds
–The data portion of a RIP
message is encapsulated into
a UDP segment with both
a

UDP

segment
,
with

both

source and destination port
numbers set to 520.
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RIPv1
RIPv1
 RIP Message Format

RIP header
-
divided into 3 fields
RIP

header

divided

into

3

fields
–Command field
•REQUEST (1)- Request either a partial
or full table update from another RIP
router.
•RESPONSE (2) - A response to a
request.
–Version field
•
1or2
•

1

or

2

–Must be zero
•Must be zero" fields provide room
for future ex
p
ansion of the
p
protocol.
 Route Entry - composed of 3
fields
–Address family identifier
•CLNS, IPX, IP etc.
–
IP address
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–Metric
RIPv1
 RIP Operation
–RIP uses 2 message types:
Request message
-
This is sent out on startup by each RIP

-
This

is

sent

out

on

startup

by

each

RIP

enabled interface
Requests all RIP enabled neighbors to send
-
Requests

all

RIP

enabled

neighbors

to

send

routing table

Response message
Response

message
-Message sent to requesting router
containing routing table
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containing

routing

table
RIP 1
RIP
v
1
 IP addresses initiall
y
divided

y
into classes
-
Class A
Class

A
-Class B
CC
-
C
lass
C
 RIP is a classful routing
protocol
-Does not send subnet
masks in routing updates
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Common RIP confi
g
uration issues
g
RIP and IGRP:
 Classful network statements only
 IOS will take subnetted networks but will translate it into
the classful network for the running-config.
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RIPv1
RIPv1
 Administrative Distance
–RIP’s default administrative distance is 120
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Basic RIPv1 Configuration

A typical topology suitable for
A

typical

topology

suitable

for

use by RIPv1 includes:
-
Three router set up
Three

router

set

up

-No PCs attached to LANs
Uf5difftIP
-
U
se o
f

5

diff
eren
t

IP

subnets
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BiRIP1Cfi ti
B
as
i
c

RIP
v
1

C
on
fi
gura
ti
on

Router RIP Command
Router

RIP

Command
–To enable RIP enter:
Router rip
at the global configuration prompt
-
Router

rip
at

the

global

configuration

prompt
-Prompt will look like R1(config-router)#
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Basic RIPv1 Configuration
Basic

RIPv1

Configuration
 S
p
ecif
y
in
g
Networks
pyg
–Use the network
command to:
-Enable RIP on all
interfaces that
belong to this
network
-
A

dvertise this
network in RIP
updates
updates

sent to other
routers
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every 30 seconds
V
erification and Troubleshooting
 Show ip Route

To verify and

To

verify

and

troubleshoot routing
-Use the following
commands:
-show ip route
show ip protocols
-

show

ip

protocols
-debug ip rip
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V ifi ti d T bl h ti
V
er
ifi
ca
ti
on an
d

T
rou
bl
es
h
oo
ti
ng

show ip protocols


show

ip

protocols
command
-Displays
routing
tl
pro
t
oco
l

configured
t
on rou
t
e
r
POP QUIZ:
POP

QUIZ:
What is the different
between the output of the
command “show i
p
route”
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p
and “show ip protocol”?
Verification and Troubleshooting
Verification

and

Troubleshooting
 Debug ip rip command
Used to display RIP routing updates as they are
-
Used

to

display

RIP

routing

updates

as

they

are

happening
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Verification and Troubleshooting
 Passive interface command
-
Used to prevent a router from sending updates through
Used

to

prevent

a

router

from

sending

updates

through

an interface

-
Example:
-
Example:

Router(config-router)#passive-interface interface-type interface-number
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Verification and Troubleshooting

Passive interfaces
Passive

interfaces
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Preventin
g
routin
g
u
p
dates throu
g
h an interface
ggp g

 Route filtering works by regulating the
routes that are entered into or advertised
out of a route table.
Lb
As a result, a route filter influences which
routes the router advertises to its
neighbors.

On the other hand routers running link
L
a
b
:

On

the

other

hand
,
routers

running

link

state protocols determine routes based
on information in the link-state database.

Route filters have no effect on link-state
advertisements or the link
state database
advertisements

or

the

link
-
state

database
.
(Tony) Route filtering could have negative
effect on the link-state routing protocol.

Using the
passive interface
command

Using

the

passive

interface
command

can prevent routers from sending routing
updates through a router interface, but
the router continues to listen and use
routing updates from that neighbor
routing

updates

from

that

neighbor
.
Keeping routing update messages from
being sent through a router interface
prevents other systems on that network
from learning about routes dynamically
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from

learning

about

routes

dynamically
.
Preventing routing updates
Preventing

routing

updates

through an interface

Again this is only half the
It will break the rip update
1

Again
,
this

is

only

half

the

story.
When you use “passive

When

you

use

“passive

interface” on a distance
vector routin
g

p
rotocol
,

y
ou
gp
,y
need to complement it with
“ip route” command.
You can use the “ip route”
command to send route update
bk blihh2
2
b
ac
k
to esta

bli
s
h
t
h
e
2
way
communication
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Automatic Summarization
Automatic

Summarization

Modified Topology

The original scenario has been
The

original

scenario

has

been

modified such that:
Three classful networks are used:
172.30.3.0
172.30.0.0/16
192.168.4.0/24
192 168 5 0/24
172.30.2.0
172.30.1.0
192
.
168
.
5
.
0/24
The 172.30.0.0/16 network is
subnetted into three subnets:
172.30.1.0/24
172.30.2.0/24
172.30.3.0/24
The following devices are part of the
172.30.0.0/16 classful network address:
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All interfaces on R1
S0/0/0 and Fa0/0 on R2
Automatic Summarization

Cfi ti Dtil

C
on
fi
gura
ti
on
D
e
t
a
il
s
-To remove the RIP routing
th f ll i
process use
th
e
f
o
ll
ow
i
ng
command
Nti
N
o rou
t

er r
i
p
-To check the configuration
use the following command
Show run
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Automatic Summarization
Automatic

Summarization
 Boundary Routers
RIP automatically summarizes classful networks
–
RIP

automatically

summarizes

classful

networks
–Boundary routers summarize RIP subnets from one
major network to another
major

network

to

another
.
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Automatic Summarization
Automatic

Summarization
Processing RIP Updates
 2 rules govern RIPv1 updates:
-If a routin
g
u
p
date and the interface it’s
gp
received on belong to the same
network then
The subnet mask of the
The

subnet

mask

of

the

interface is applied to the
network in the routing update
If a routing update and the interface it
’
s
-
If

a

routing

update

and

the

interface

it s

received on belong to a different
network then
Th l f l b k f h

Th
e c
l
ass
f
u
l
su
b
net mas
k
o
f
t
h
e
network is applied to the
network in the routing update.
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Automatic Summarization

Sending RIP Updates

Sending

RIP

Updates
–RIP uses automatic summarization to reduce the
size of a routing table
size

of

a

routing

table
.
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AiSii
A
utomat
i
c
S
ummar
i
zat
i
on

Advantages of automatic

Advantages

of

automatic

summarization:
-
The size of
-
The

size

of

routing updates is
reduced
-Single routes are
used to represent
multiple routes
which results in
faster lookup in the
faster

lookup

in

the

routing table.
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