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RIP version 1
Routing Protocols and
Concepts – Chapter 5
Sandra Coleman, CCNA, CCAI
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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

Turquoise text is test-worthy!
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RIPv1
 RIP Characteristics
-Oldest distance vector protocol
-A classful, Distance Vector (DV) routing protocol
-Metric = hop count
-Routes with a hop count > 15 are unreachable
-16 hops = infinity
-Updates are broadcast every 30 seconds
-Calculates metrics using the Bellman Ford algorithm
-Data portion is encapsulated into UDP segment
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RIPv1
 RIP Message Format
 RIP header - divided into
3 fields
-Command field
-Version field
-Must be zero
 Route Entry - composed
of 3 fields
-Address family
identifier
-IP address
-Metric (hops)
 RIPv2 uses most of the
‘must be zero’ space
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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
-A router either uses the SM
configure on the local interface or
applies the default subnet mask
of the class
-Can’t support discontiguous
networks or VLSM
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RIPv1
 Administrative Distance
–RIP’s default AD is 120 which makes it the leastpreferred routing protocol (all others have a lower
AD)
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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:
Notice that typing
Router ? At the
prompt
Will show you ALL
Available routing
protocols
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-Router rip at the global configuration prompt
-Prompt will look like R1(config-router)#
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Removing RIP
 To completely remove RIP routing from a router, just
type in the following command:
router(config)#no router rip
 This command will STOP all rip processes and erase
all existing RIP configurations!
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Basic RIPv1 Configuration
 Specifying Networks (You have to
be able to do this on the test!)
–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
-If you enter an IP address
instead of a network address,
RIP will include all interfaces in
that CLASSFUL network in the
routing process
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Verification and Troubleshooting
 To verify and
troubleshoot routing
-Use the following
commands:
-show ip route
-show ip protocols
-debug ip rip
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Routing tables
 You will have to look at a topology and pick from a list
routes that would appear in a routing table for a specific
router in that topology. One thing you really need to
pay attention to is whether it is a connected or RIP
route and look at the metric…make sure it is correct!
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Verification and Troubleshooting
 show ip protocols
command
-Displays routing
protocol
configured on
router
Be able to interpret
these on a test!
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Marking invalid routes
Refer to the routing table below. Notice the timer SINCE the
last update. How long would it take to mark 192.168.1.0
INVALID if it went down? Invalid timer is 180 seconds.
Subtract the time since the last update (5 seconds) and you
get the answer! You will have to do this on the test as well!
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Verification and Troubleshooting
 Debug ip rip command (5.3.3 – online curriculum)
-Used to display RIP routing updates as they are
happening - USE undebug all to turn off ALL
debugging!
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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
Router(config-router)#passive-interface fa 0/0
 When would you use this command? If you have an interface that has only
END-USERS (LAN-Ethernet connection) connected, there is no need to
broadcast routing updates to end-users. It WASTES bandwidth!
 We only need to send routing update out interfaces where OTHER routers are
found…but we do want the LANS to be included in the updates.
 Passive interface prevents the transmission of routing updates through a router
interface but still allows that network to be advertised to other routers
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Verification and Troubleshooting
 Passive interfaces
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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
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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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.
–Because boundary routers summarize RIP subnets from one major
network to the other, updates for the 172.30.1.0, 172.30.2.0 and
172.30.3.0 networks will automatically be summarized into 172.30.0.0
when sent out R2's Serial 0/0/1 interface.
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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.
RIPv1 DOES NOT send subnet mask
information in its updates!
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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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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 (AKA Gateway of last resort)
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
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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.
Indicates a
‘default –
information
originate’
command
from R2
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Where to put default routes?
 Default routes (0.0.0.0) and the ability to propagate
these routes to others lies with the border router.
 What is a border router? It is the router in your
company that connects to your ISP.
 So these commands belong on the border router!
ip route 0.0.0.0 0.0.0.0 s0/0/1
Default-information originate
 You should NEVER exchange routing updates with an
ISP. You only set up a static route to them. Otherwise,
you end up with a HUGE routing table, and all outgoing
traffic still goes there anyway!
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Equal Cost Paths
When you see routing table entries that have the same
network listed with 2 different outgoing interfaces…know
that these are 2 EQUAL COST PATHS.
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Summary: Commands used by RIP
Command
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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Ch. 5 is OVER…Hallelujah!
•
Study Guide –
• Packet tracer exercise 5-2 pg. 200-201 (homework)
•
Labs –
• 5-1 (scenario A & B only) – In class today! If you don’t finish, Do
scenario B on Packet Tracer for extra practice
•
•
Online test for ch. 5 will be on until Sunday, Feb 24, 2013 @ midnight!
Test on ch. 5 will be on Monday, Feb 25, 2013
•
We will do EVERYTHING we can in class today…anything left, is
homework and should be done and emailed to me before next Monday
morning.
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