Routing Protocols and Concepts: Chapter 5 doc

Topics ® RIPv1: Distance Vector, Classful Routing Protocol * Background and Perspective *« RIPv1 Characteristics and ® Verification and Troubleshooting * Verifying RIP: show ip rout

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Topics

® RIPv1: Distance Vector, Classful

Routing Protocol

* Background and Perspective

*« RIPv1 Characteristics and

® Verification and Troubleshooting

* Verifying RIP: show ip route

* Verifying RIP: show ip

* Processing RIP Updates

* Sending RIP Updates

* Advantages and |

Disadvantages of Automatic Summarization

Default Route and RIPv1

* Modified Topology C

* Propagating the Default Route

in RIPv1

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RiPvi: A Distance Vector,

Classful Routing Protocol

® Background and Perspective

@ RIPv1 Characteristics and Message Format

® RIP Operation

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RIPv1: Distance Vector, Classful Routing Protocol

Classful RIP IGRP

Classless RIPv2 EIGRP IS-IS

EIGRP for IS-IS for

|

Pv6 RIPng IPv6 OSPFv3 IPv6

Highlighted routing protocols are the focus of this course

® The first protocol used was Routing Information Protocol (RIP)

@® RIP still popular: simple and widespread support

@ Why learn RIP?

Still in use today

Help understand fundamental concepts and comparisons of

protocols

¢ such as classful (RIPv1) and classless (RIPv2)

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Background and Perspective

Networking Protocols Development RIP Development

Early 1970s

Mid 1970s TCP/IP Early Xerox PARC Universal Gateway Information

Development Protocol (PUP) Protocol (GWINFO)

Xerox Network System Routing Information Late 1970s (XNS) Protocol

Early 1980s TCP/IP Standardized Berkeley Software Routed Daemon

y RFCs 791, 793 Distribution (UNIX BSD 4.2) (“route-dee”)

1994 RFC 1723: RIPv2

@ RIP is not a protocol “on the way out.”

® In fact, an IPv6 form of RIP called RIPng (next generation) is now available

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Background and

Perspective

Network Working Group

Routing Information Protocol

Status of this Memo

Rutgers University

June 1988

This RFC describes an existing protocol for exchanging routing

used as a basis for developing gateway software for use in the

Table of Contents

@ Charles Hedrick wrote RFC 1058 in 1988, in which he documented

the existing protocol and specified some improvements

@® RFC 1058 can be found at http://www.iett.org/ric/ric1 058.txt

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RIPvi Characteristics and Message Format

« Distance vector routing protocol

* Metric: hop count

* Advertised routes with hop counts greater than 15 are

considered unreachable

* Response messages (routing table updates) are broadcast every

30 seconds (RIPv2 uses multicasts)

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Data Link Frame

Header

IP Packet Header

UDP Segment

Header

RIP Message (512 Bytes: Up to 25 Routes)

Data Link Frame

MAC Source Address = Address of Sending Interface

MAC Destination Address = Broadcast: FF-FF-FF-FF-FF-FF

IP Packet

IP Source Address = Address of Sending Interface

IP Destination Address = Broadcast: 255.255.255.255 Protocol Field = 17 for UDP

UDP Segment

Source Port = 520 Destination Port = 520

oa

Next slide ~<

RIP Message Command: Request (1); Response (2) Version = 1

Address Family ID = 2 for IP

Routes: Network IP Address Metric: Hop Count

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Header

Data Link Frame IP Packet Header | UDP Segment Header (512 Bytes; Up to 25 Routes) RIP Message

Address Family Identifier

IP Address

Metric

Description

| for a Request or 2 for a Response

| for RIPv1 or 2 for RIPv2

2 for IP unless a Request is for the full routing table, in which case the field is set to 0

The address of the destination route, which can be a network, subnet, or host address

Hop count between | and 16 The sending router increases the metric before sending out the message.

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RIP Message Format: Route Entry

RIP Message (512 Byles; Up to 25 Routes)

Data Link Frame

IP Packet Header | UDP Segment Header Header

@ Each Route Entry (three fields):

Address Family Identifier (set to 2 for IP unless a router is requesting

a full routing table, in which case the field is set to 0)

IP Address: Network address of an advertised route

Metric: How many hops to get to this network via this router

(incremented by each router)

® One RIP update can contain up to 25 route entries.

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RIP Operation

Address Family Identifier (2 = IP) (2) \

IP Address (Network Address)

1 Each RIP-configured interface sends out a Request message

Asking for their complete routing tables

2 A Response message is sent back by RIP-enabled neighbors

lf new route: Installs in routing table

lf existing route: Replace if better hop count

@® Siartup router then sends a triggered update out all RlIP-enabled interfaces

containing its own routing table so that RIP neighbors can be informed of

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IP Address Classes and Classful Routing

e Classful routing protocol

e Does not send subnet mask in update

@ A router either uses the subnet mask: (discussed later)

° configured on a local interface or

° applies the default classful subnet mask

Class A Address Range: 0.0.0.0 to 126.255.255.255

Class B Address Range: 128.0.0.0 to 191.255.255.255 Class C Address Range: 192.0.0.0 to 223.255.255.255

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Routing Protocol is “rip”

Routing Information Sources:

Gateway Distance Last Update

192.168.6.2 120 00:00:10

@ RIP has a default administrative distance of 120

@ When compared to other interior gateway protocols, RIP is the least-

preferred routing protocol

Note: This is irrelevant because you usually do not run multiple routing protocols in the same domain, and even if you did you can modify these

AD values

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Basic RIPv1 Configuration

® RIPv1 Scenario A

® Enable RIP: router rip Command

® Specifying Networks

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@ Notice that this topology uses five Class C network addresses

@ Remember, RIPv1 is a classful routing protocol

@ We will see that the class of the network is used by RIPv1 to determine the

subnet mask

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Enabling RIP: router rip Command

Exterior Gateway Protocol (EGP)

ISO IS-IS IGRP for OSI networks Mobile routes

On Demand stub Routes

Rl (config-router) #

@® Enter router configuration mode for RIP, enter router rip atthe

global configuration prompt

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Enabling RIP: router rip Command

Does not directly start the RIP process

Provides access to configure routing protocol settings

® No routing updates are sent until additional commands are

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@ To enable RIP routing for a network, use the network command in

router configuration mode

@ Enter the classful network address for each directly connected

network

18

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® The network command performs the following functions:

Enables RIP on all interfaces that belong to a specific network

e Associated interfaces will now both send and receive RIP

updates

Advertises the specified network in RIP routing updates sent to other routers every 30 seconds

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Specifying Networks Only directly connected classful network

® If you enter a subnet or host IP address, IOS automatically converts

it to a classful network address

@ For example, if you enter the command network 192.168.1.32,

the router will convert it to network 192.168.1.0

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R1(conflg) # router rip

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Verification and

Troubleshooting

®@ Verifying RIP: show ip route

@ Verifying RIP: show ip protocols

® Verifying RIP: debug ip rip

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Verifying RIP: show ip route Command

C 192.168.1.0/24 is directly connected, FastEthernet0/0

C 192.168.2.0/24 is directly connected, Serial0/0/0

R 192.168.3.0/24 [120/1] via 192.168.2.2, 00:00:02, Serial0/0/0

® AnRin the output indicates RIP routes

@® Because this command displays the entire routing table, including

directly connected and static routes, it is normally the first command

used to check for convergence

@ Routes might not immediately appear when you execute the

command because networks take some time to converge

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R 192.168.5.0/24 [120/1] via 192.168.4.1, 00:00:12, Serial0/0/1

R 192.168.1.0/24 [120/1] via 192.168.2.1, 00:00:24, Serial0/0/0

C 192.168.3.0/24 is directly connected, FastEthernet0/0

24

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R Identifies the source of the route as RIP

192.168.5.0 Indicates the address of the remote network

{24 Indicates the subnet mask used for this network

[120/2] Shows the administrative distance (120) and the metric (2 hops)

via 192.168.2.2, Specifies the address of the next-hop router (R2) to send traffic to for

the remote network

00:00:23, Specifies the amount of time since the route was updated (here, 23 sec-

onds) Another update is due in 7 seconds

Serial0/0/0 Specifies the local interface through which the remote network can be

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Routing Protocol is "rip"

Sending updates every 30 seconds, next due in 23 seconds

Invalid after 180 seconds, hold down 180, flushed after 240

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Redistributing: rip

Default version control: send version 1, receive any version

Interface Send Recv Triggered RIP Key-chain

192.168.3.0 @ Atleast one active interface with an associated network

192.168.4.0 command is needed before RIP routing will start

192.168.2.1 120 00:00:18

192.168.4.1 120 00:00:22

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“Routing Protocol is "rip"

Sending updates every 30 seconds, next due in 23 seconds

Redistributing: rip

PFastEthernet0/0 1 1 2 Serial0/0/0 1 1 2 Serial0/0/1 1 1 2

Automatic network summarization is in effect

Maximum path: 4

Routing for Networks: @® [hese are the timers that show when the next

192.168.2.0 round of updates will be sent out from this

hes tee sáng router—23 seconds from now, in the example

Gateway Distance Last Update 192.168.2.1 120 00:00:18 192.168.4.1 120 00:00:22 Distance: (default is 120) 28

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Verifying RIP: show ip protocols Command

R2#show ip protocols

(1) —Routing Protocol is "rip’

@{ Sending updates every 30 seconds, next due in 23 seconds

Redistributing: rip

Maximum path: 4 ¬ SỐ

Routing for Networks: ® Thịs information relates to filtering updates and

192.168.2.0 redistributing routes, if configured on this router

192.168.3.0 @ Filtering and redistribution are both CCNP-level

192.168.2.1 120 00:00:18 192.168.4.1 120 00:00:22

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®{ Incoming update filter list for all interfaces is not set

Redistributing: rip

Maximum path: 4

Routing for Networks: ® Information about which RIP version ts

(7) 192.168.2.1 120 00:00:18

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Maximum path: 4 @ Router R2 is currently summarizing at the classful network

Routing for Networks: boundary

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Redistributing: rip

Maximum path: 4

Routing for Networks: ® Classful networks configured with the network

192.168.3.0 @ These are the networks that R2 will include in its

192.168.4.0 RIP updates (with other learned routes)

192.168.2.1 120 00:00:18 192.168.4.1 120 00:00:22

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Invalid after 180 seconds, hold down 180, flushed after 240 Outgoing update filter list for all interfaces is not set

®{ Incoming update filter list for all interfaces is not set

Redistributing: rip

(4) FastEthernet0/0 1 1 2

Serial0/0/0 1 1 2

Serlial0/0/1 1 1 2

® { Automatic network summarization is in effect

Maximum path: 4 @ RIP neighbors

Routing for Networks: ® Gateway: Next-hop IP address of the neighbor that is sending R2

(6) @ Distance is the AD that R2 uses for updates sent by this neighbor

192.168.3.0 @ Last Update is the seconds since the last update was received

192.168.4.0 from this neighbor

(@) 192.168.2.1 120 00:00:18

192.168.4.1 120 00:00:22

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Verifying RIP: debug ip rip Command

R2#debug ip rip RIP protocol debugging is on

received vl update from 192.168.2.1 on Seriald/0/0 192.162.1.0 in 1 hops

received vl update from 192.168.4.1 on Seriald/0/1 192.162.5.0 in 1 hops

sending vl update to 255.255.255.255 via FastEthernetd0/0 (192.168.3.1)

entrie

.168.1.0 168.2.0 -168.4.0 168.5.0 sending vl update

(192.168.4.2)

build update entries

metric

metric metric

build update entries network 192.168.3.0 metric l network 192.168.4.0 metric l

® The debug command is a useful tool to help diagnose and resolve

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@ Update coming in from R1 on interface Serial 0/0/0

® Ri only sends one route: 192.168.1.0

@ No other routes are sent because doing so would violate the split horizon

rule

R1 is not allowed to advertise networks back to R2 that R2 previously sent to R1

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192.1682 0/24 192.1684.024

192.168.1.0/24 1 S0/0O

— Faoo S3 Z<Ò DpcE bá | i Se Fado —_

@ The next update that is received is from R3

@ Because of the split horizon rule, R3 only sends one route: the 192.168.5.0

network

1 192.168.5.0/24

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RIP: sending vl update to 255.255.255.255 via FastEthernet0/0

(192.168.3.1) RIP: build update entries

network 192.168.1.0 metric network 192.168.2.0 metric network 192.168.4.0 metric

2

1

1 network 192.168.5.0 metric 2

Includes the entire routing table except for network 192.168.3.0,

FaO/O

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RIP: sending vl update to

network 192.168.1.0 network 192.168.2.0 network 192.168.3.0

255.255.255.255 via Serial0/0/1

metric 2 metric l

s +

Three routes are included

R2 does not advertise t he network R2 and R3 share, nor does It advertise the 192.168.5.0 network because of split horizon

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RIP: sending vi update to 255.255.255.255 via Serial0/0/0

network 192.168.3.0 metric 1 network 192.168.4.0 metric l network 192.168.5.0 metric 2

Three routes are included

R2 does not advertise the network that R2 and R1 share, nor does It advertise the 192.168.1.0 network because of split horizon

@ In another 30 seconds, all the debug output will repeat (every 30 seconds) 39

192.1685.024

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To stop monitoring no debug ip rip Of undebug all

But do you see a way to optimize RIP routing on R2?

Does R2 need to send updates out FastEthernet 0/0?

You will see in the next topic how to prevent unnecessary updates

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Tiêu đề	Routing Protocols and Concepts: Chapter 5 Doc
Trường học	Unknown School
Chuyên ngành	Networking and Routing Protocols
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