Transcript RIP version 1

RIP version 1
Routing Protocols and Concepts – Chapter 5
Modified by Tony Chen
06/10/2008
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Notes:

If you see any mistake on my PowerPoint slides or if
you have any questions about the materials, please
feel free to email me at [email protected].
Thanks!
Tony Chen
College of DuPage
Cisco Networking Academy
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Objectives

Describe the functions, characteristics, and operation
of the RIPv1 protocol.

Configure a device for using RIPv1.

Verify proper RIPv1 operation.

Describe how RIPv1 performs 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 protocol
developed at Xerox, called Gateway
Information Protocol (GWINFO).
 With the development of Xerox Network
System (XNS), GWINFO evolved into
RIP.
 It later gained popularity because it was
implemented in the Berkeley Software
Distribution (BSD) as a daemon named
routed (pronounced "route-dee", not
"rout-ed").
 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.
 Since then, RIP has been improved with
RIPv2 in 1994 and with RIPng in 1997.
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IPv6 form of RIP called
RIPng (next generation) is
now available
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RIPv1
 RIP Characteristics
–A classful, Distance Vector
(DV) routing protocol
–Metric = hop count
–Routes with a hop count > 15
are unreachable
–Updates are broadcast every
30 seconds
–The data portion of a RIP
message is encapsulated into
a UDP segment, with both
source and destination port
numbers set to 520.
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RIPv1
 RIP Message Format
 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
•1 or 2
–Must be zero
•Must be zero" fields provide room
for future expansion of the
protocol.
 Route Entry - composed of 3
fields
–Address family identifier
•CLNS, IPX, IP etc.
–IP address
–Metric
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RIPv1
 RIP Operation
–RIP uses 2 message types:
Request message
-This is sent out on startup by each RIP
enabled interface
-Requests all RIP enabled neighbors to send
routing table
Response message
-Message sent to requesting router
containing routing table
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RIPv1
 IP addresses initially divided
into classes
-Class A
-Class B
-Class C
 RIP is a classful routing
protocol
-Does not send subnet
masks in routing updates
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Common RIP configuration issues
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
 Administrative Distance
–RIP’s default administrative distance is 120
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Basic RIPv1 Configuration
 A typical topology suitable for
use by RIPv1 includes:
-Three router set up
-No PCs attached to LANs
-Use of 5 different IP
subnets
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Basic RIPv1 Configuration
 Router RIP Command
–To enable RIP enter:
-Router rip at the global configuration prompt
-Prompt will look like R1(config-router)#
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Basic RIPv1 Configuration
 Specifying Networks
–Use the network
command to:
-Enable RIP on all
interfaces that
belong to this
network
-Advertise this
network in RIP
updates
sent to other
routers
every 30 seconds
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Verification and Troubleshooting
 Show ip Route
 To verify and
troubleshoot routing
-Use the following
commands:
-show ip route
-show ip protocols
-debug ip rip
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Verification and Troubleshooting
 show ip protocols
command
-Displays
routing
protocol
configured
on router
POP QUIZ:
What is the different
between the output of the
command “show ip route”
and “show ip protocol”?
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Verification and Troubleshooting
 Debug ip rip command
-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
an interface
-Example:
Router(config-router)#passive-interface interface-type interface-number
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Verification and Troubleshooting
 Passive interfaces
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Preventing routing updates through an interface
 Route filtering works by regulating the
routes that are entered into or advertised
out of a route table.
Lab:
As a result, a route filter influences which
routes the router advertises to its
neighbors.
 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.
(Tony) Route filtering could have negative
effect on the link-state routing protocol.
 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.
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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Preventing routing updates
through an interface
1
It will break the rip update
2
You can use the “ip route”
command to send route update
back to establish the 2 way
communication
 Again, this is only half the
story.
When you use “passive
interface” on a distance
vector routing protocol, you
need to complement it with
“ip route” command.
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Automatic Summarization
Modified Topology
 The original scenario has been
modified such that:
Three classful networks are used:
172.30.0.0/16
172.30.1.0
192.168.4.0/24
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:
All interfaces on R1
S0/0/0 and Fa0/0 on R2
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172.30.3.0
172.30.2.0
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Automatic Summarization
 Configuration Details
-To remove the RIP routing
process use the following
command
No router rip
-To check the configuration
use the following command
Show run
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Automatic Summarization
 Boundary Routers
–RIP automatically summarizes classful networks
–Boundary routers summarize RIP subnets from one
major network to another.
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Automatic Summarization
Processing RIP Updates
 2 rules govern RIPv1 updates:
-If a routing update and the interface it’s
received on belong to the same
network then
The subnet mask of the
interface is applied to the
network in the routing update
-If a routing update and the interface it’s
received on belong to a different
network then
The classful subnet mask of the
network is applied to the
network in the routing update.
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Automatic Summarization
 Sending RIP Updates
–RIP uses automatic summarization to reduce the
size of a routing table.
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Automatic Summarization
 Advantages of automatic
summarization:
-The size of
routing updates is
reduced
-Single routes are
used to represent
multiple routes
which results in
faster lookup in the
routing table.
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Automatic Summarization
 Disadvantage of Automatic Summarization:
-Does not support discontiguous networks
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Automatic Summarization
 Discontiguous
Topologies do not
converge with RIPv1
 A router will only
advertise major
network addresses
out interfaces that do
not belong to the
advertised route.
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Automatic Summarization
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Default Route and RIPv1
 Modified Topology: Scenario C
 Default routes
Packets that are not defined specifically in a routing
table will go to the specified interface for the default
route
Example: Customer routers use default routes to
connect to an ISP router.
Command used to configure a default route is
ip route 0.0.0.0 0.0.0.0 s0/0/1
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Default Route and RIPv1
* pictures and
tables does
not match.
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Default Route and RIPv1
 Propagating the Default Route in RIPv1
 Default-information originate command
-This command is used to specify that the router is to originate
default information, by propagating the static default route in
RIP update.
* pictures and
tables does
not match.
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Default route with RIP
Centre#show
ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile,
Gateway of last resort is not set
Mobile#sho ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile,
R
192.168.4.0/24 [120/1] via 192.168.2.1, 00:00:11, Serial0
R
192.168.1.0/24 [120/1] via 192.168.2.1, 00:00:11, Serial0
C
192.168.2.0/24 is directly connected, Serial0
C
192.168.3.0/24 is directly connected, Ethernet0
Setup up a default route on the Centre router
Centre(config)#ip route 0.0.0.0 0.0.0.0 loopback0
Centre(config)#router rip
Centre(config-router)#default-information originate
Centre#sh ip route
Codes: C - connected, S - static, * - candidate default
Gateway of last resort is 0.0.0.0 to network 0.0.0.0
C
172.16.1.1 is directly connected, Loopback0
R
192.168.4.0/24 [100/8576] via 192.168.2.1, 00:00:22, Serial0
R
192.168.5.0/24 [120/2] via 192.168.2.1, 00:00:22, Serial0
S* 0.0.0.0/0 is directly connected, Loopback0
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Gateway of last resort is not set
R
192.168.4.0/24 [120/1] via 192.168.1.1, 00:00:04, Serial0
C
192.168.5.0/24 is directly connected, Ethernet0
C
192.168.1.0/24 is directly connected, Serial0
R
192.168.2.0/24 [120/1] via 192.168.1.1, 00:00:04, Serial0
R
192.168.3.0/24 [120/2] via 192.168.1.1, 00:00:04, Serial0
Mobile#sho ip route
Codes: C - connected, S - static, * - candidate default - RIP,
Gateway of last resort is 192.168.1.1 to network 0.0.0.0
R
192.168.4.0/24 [120/1] via 192.168.1.1, 00:00:09, Serial0
C
192.168.5.0/24 is directly connected, Ethernet0
C
192.168.1.0/24 is directly connected, Serial0
R
192.168.2.0/24 [120/1] via 192.168.1.1, 00:00:04, Serial0
R
192.168.3.0/24 [120/2] via 192.168.1.1, 00:00:09, Serial0
R* 0.0.0.0/0 [120/2] via 192.168.1.1, 00:00:09, Serial0
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Summary
 RIP characteristics include:
Classful, distance vector routing protocol
Metric is Hop Count
Does not support VLSM or discontiguous subnets
Updates every 30 seconds
 Rip messages are encapsulated in a UDP segment
with source and destination ports of 520
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Summary: Commands used by RIP
Command
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Command’s purpose
Rtr(config)#router rip
Enables RIP routing process
Rtr(config-router)#network
Associates a network with a RIP routing process
Rtr#debug ip rip
used to view real time RIP routing updates
Rtr(config-router)#passive-interface fa0/0
Prevent RIP updates from going out an interface
Rtr(config-router)#default-information originate
Used by RIP to propagate default routes
Rtr#show ip protocols
Used to display timers used by RIP
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