Routing Protocols and Concepts: Chapter 7 potx

@® RIPv2, it is ideal for explaining the differences between a classful routing protocol RIPv1 and a classless routing protocol RIPv2... Next-hop addresses included in the routing updat

« RIPv2 and CIDR

® Verifying and Troubleshooting

* Common RIPv2 Issues

® Configuring RIPv2 * Authentication

* Enabling and Verifying RIPv2

* Auto-Summary and RIPv2

* Disabling Auto-Summary in

RIPv2

* Verifying RIPv2 Updates

RIPv1 Limitations

® RIPv1: Topology Limitations

® HIPv1: Discontiguous Networks

® RIPv1i: No VLSM Support

Note on Classful Routing Protocols, RIPv1 limitations

@ The first part of this presentation discusses the limitations of classful

routing protocols such as RIPv1

® RIPvi is used as an example, so we can see how RIPv2 a classless

routing protocol does not have these same limitations

® Classful routing protocols have three major limitations:

* Does not support discontiguous networks

* Does not support VLSM

* Does not support CIDR

6 |Instead of just “memorizing” these facts, we will demonstrate and

“understand” why a classful routing protocol has these limitations.

RIPv1: Distance Vector, Classess Routing Protocol

EIGRP for IS-IS for

IPv6 RIPng IPv6 OSPFv3 IPv6

Highlighted routing protocols are the focus of this course

@ RIP Version 2 (RIPv2) is defined in RFC 1728

RIPv2 is the first classless routing protocol discussed in this book

@ RIPv2 has lost popularity when compared to other routing protocols such as EIGRP, OSPF and IS-IS

@® RIPv2, it is ideal for explaining the differences between a classful

routing protocol (RIPv1) and a classless routing protocol (RIPv2).

OSPF v2 RIP v2 RIPng

EGP IGRP RIPv1 IS-IS | EIGRP BGP | OSPFv3 IS-ISv6

5 EIGRP for IS-IS for IPv6 RIPng IPv6 OSPFv3 IPv6

Highlighted routing protocols are the focus of this course

@® RIiPv2 is actually an enhancement of RIPv1's features and extensions

rather than an entirely new protocol

Next-hop addresses included in the routing updates

Use of multicast addresses in sending updates

Authentication option available

@ Both versions of RIP share the following features and limitations:

Use of hold-down and other timers to help prevent routing loops

Use of split horizon and 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 hops, with the hop count of 16 signifying

10.1.0.0/16

192.168.0.0/24 192.168.1.0/24

® |nadiscontiguous network, a classful major network address, such as

172.30.0.0/16, is separated by one or more other major networks

® 172.30.0.0/16 is divided by the networks:

209.165.200.228/30

209.165.200.232/30

@ Classful routing protocols do not include enough routing information to

route properly for discontiguous networks

172 3.110.024

® H2: static summary route to the 192.168.0.0/16 network

Redistribution - |nject static route(s) into routing protocol updates

@® For now, this summary route will cause problems with RIPv1 because:

192.168.0.0/16 is not a major classful address (192.168.0.0/24)

Includes all the /24 versions of 192.168.0.0/16

® H1 and R3 contain VLSM networks

® Both Ri and R3 are configured with /24 subnets of the 172.30.0.0/16

network

® R23: 172.30.200.0/24 subnetted again, using the first 4 bits for subnets and

the last 4 for hosts

© 172.30.200.16/28 and 172.30.200.32/28

VLSM

(0 |1723000 | 172.90.0.1 to 172.30.0.254 Assigned to Ri Fad/0

® 5: 172.30.200.0/24 subnetted agaIn, using the first 4 bits for

subnets and the last 4 for hosts

® 172.30.200.16/28 and 172.30.200.32/28 10

Private Addresses and Cisco Example Addresses

10.1.0.0/16

192.168.0.0/24 192.168.1.0/24

e Used to emulate an interface

e Can be assigned an IP address

° Specific purposes with some routing protocols such as OSPF (later)

@ A loopback interface can be:

° pinged

e subnet advertised in routing updates

@ Ideal for simulating multiple networks attached to the same router 12

RIPv1 Topology Limitations

config)# ip route 192.168.0.0 255.255.0.0 nul10

config)# router rip

Static Routes and 198

@ For Lab purposes:

The static summary route 192.168.0.0/16 does not actually exist

To simulate this static route, we will use a null interface as the exit interface

You do not need to enter commands to create or configure the null

interface

lt is always up but does not forward or receive traffic

Traffic sent to the null interface is discarded

The static route on R2 is using a/16 mask to summarize all 256 networks

14

255.255.0.0 nul10

R2(config-router)# redistribute static

Sova

fe

Is static route being sent via RIPv1 with other RIPv1 routes?

@® Redistribution involves taking the routes from one routing source and

sending those routes to another routing source

@ Routes can only be redistributed into a dynamic routing protocol

Dynamic routing protocol to a different dynamic routing protocol

Static routes to a dynamic routing protocol

Directly connected networks to a dynamic routing protocol

@ Want R2 io redistribute our static route (192.168.0.0/16) by importing the

route into RIPv1 and then sending it to R1 and R3 using the RIPv1 process

@® We will see whether this is indeed happening, and if not, why not

15

Verifying and Testing waman, fe

R2# ping 172.30.1.1

Type escape sequence to abort

Sending 5, 100-byte ICMP Echos to 172.30.1.1, timeout is 2 seconds:

!UI.!

Success rate is 60 percent (3/5), round-trip min/avg/max = 28/29/32 ms

R2# ping 172.30.100.1

Type escape sequence to abort

Sending 5, 100-byte ICMP Echos to 172.30.100.1, timeout is 2 seconds:

!UI.!

Success rate is 60 percent (3/5), round-trip min/avg/max = 28/28/28 ms

R2 #

@ Whenever R2 pings any of the 172.30.0.0 subnets on R1 or R82, only

about 50 percent of the pings are successful 16

R1# ping 10.1.0.1

Type escape sequence to abort

Sending 5, 100-byte ICMP Echos to 10.1.0.1, timeout is 2 seconds:

Success rate is 100 percent (5/5),round-trip min/avg/max = 28/28/28 ms

R1l# ping 172.30.100.1

Type escape sequence to abort

Sending 5, 100-byte ICMP Echos to 172.30.100.1, timeout is 2 seconds:

Success rate is 0 percent (0/5)

R1#

@ Ri is able to ping 10.1.0.1 but is unsuccessful when attempting to

ping the 172.30.100.1 interface on R3 17

Verifying and Testing

Connectivity cs =: Fao > DCE Xe Tin — |

Type escape sequence to abort

Sending 5, 100-byte ICMP Echos to 10.1.0.1, timeout is 2 seconds:

Success rate is 100 percent (5/5),round-trip min/avg/max = 28/28/28 ms

R3# ping 172.30.1.1

Type escape sequence to abort

Sending 5, 100-byte ICMP Echos to 172.30.1.1, timeout is 2 seconds:

Success rate is 0 percent (0/5)

R3#

@® RG is able to ping 10.1.0.1 but is unsuccessful when attempting to

ping the 172.30.1.1 interface on R1

@ As you can see, there is an obvious problem when trying to

RIPv1: Discontiguous Networks

RIPv1 Message Format

@ RIPvi on both Routers R1 and R8 will summarize their 172.30.0.0

subnets to the classful major network address of 172.30.0.0 when

sending routing updates to R2 90

Examining the Routing Tables

C 209.165.200.232 is dđirectly connected, Serial0/0/1

C 209.165.200.228 is directly connected, Serial0/0/0

10.0.0.0/16 is subnetted, 1 subnets

10.1.0.0 is directly connected, FastEthernet0/0

S 192.168.0.0/16 is directly connected, Null0

@ R2 has two equal-cost routes to the 172.30.0.0/16 network

H1 and R3 are sending H2 a RIPv1 update for the 172.30.0.0 network with a metric of 1 hop

@ R2’s routing table only contains the major classful network address of

172.30.0.0 and adds the Class B subnet mask of /16

21

RIP: sending vl update to 255.255.255.255 via Serial0/0/1

(209.165.200.233)

RIP: build update entries

network 10.0.0.0 metric 1 subnet 209.165.200.228 metric 1

® R2 is receiving two 172.30.0.0 equal-cost routes with a metric of 1 hop:

one route on Serial 0/0/0 from R1 and

the other route on Serial 0/0/1 from R3

@ Also notice that the subnet mask is not included with the network

209.165.200.232 [120/1] via 209.165.200.229, 00:00:16,Serial0/0/0 209.165.200.228 is directly connected, Serial0/0/0

R1 does not send R2 those subnets

R1 and R3 are boundary routers only sending the summarized 172.30.0.0 Result, R2 only Knows about the 172.30.0.0/16 classful network and is

Determining the mask and network address

® Receiving an Update: Determining subnet mask for routing table

« What is the major classful network address of the receiving interface?

> What is the major classful network address of the network in the routing

update?

« Are they the same major classful network address?

* Yes: Apply subnet mask of the receiving interface for this network address in the routing table

¢ No: Apply classful subnet mask for this network address in the routing table

@ Sending an Update: Determining whether or not to summarize route sent

* What is the major classful network address of the sending interface?

* What is the major classful network address of the network in the routing

update?

* Are they the same major classful network address?

¢ Yes: Send subnet network address

¢« No: Send summary address — the classful network address

24

Example 1

20

Example 2

2/

Example 3

29

Example 4

31

Example 5

33

Example 6

35

> Apply /16 classful mask

(route not used)

Apply /16 classful mask <

36

How Classful Routing

Protocols Determine

Subnet Masks

172.30 110 Of24

38

Protocols Determine Semmens Seems | Ab nec Ged

Route ®© 4 ° Subnet Masks

VLSM issues: will discuss next

39

@® When RIPv1 on R3 sends its 172.30.0.0 subnets out its exit

interface FastEthernet 0/0, it will only include those 172.30.0.0

subnets with the same subnet mask as the exit interface

41

RIPv1: No CIDR Support

R2(config)# ip route 192.168.0.0 255.255.0.0 null0

R2(config)# router rip

R2(config-router)# redistribute static

C 209.165.200.232 is dđirectly connected, Serial0/0/1

C 209.165.200.228 is directly connected, Serial0/0/0

10.0.0.0/16 is subnetted, 1 subnets

S 192.168.0.0/16 is directly connected, Null0

@ We see the static route, let's see if it is be sent in RIPv1 updates

with the other RIPv1 routes

42

sending vl update to 255.255.255.255 via Serial0/0/1

(209.165.200.233)

build update entries

network 10.0.0.0 metric 1 subnet 209.165.200.228 metric 1

® R2 is not including the 192.168.0.0/16 route in its RIPv1 updates

to either R1 or R3

44

RIPv1: No CIDR Support

R2(config)# ip route 192.168.0.0 255.255.0.0 null0

R2(config)# router rip

R2(config-router)# redistribute static

The static route 192.168.0.0 has a /16 mask

This is fewer bits than the classful Class C mask of /24

RIPv1 and other classful routing protocols cannot support CIDR

routes that are summarized routes with a smaller subnet mask than

the classful mask of the route

RIPv1 ignores these supernets in the routing table and does not include

them in updates to other routers

This ts because the receiving router would only be able to apply the

larger /24 classful mask to the update and not the shorter /16 mask

Note:

lf the 192.168.0.0 static route were configured with a /24 mask or

greater, this route would be included in the RIP updates

The receiving routers would apply the classful /24 mask to this update 45

Configuring RIPv2

® Enabling and Verifying RIPv2

® Auto-Summary and RIPv2

® Disabling Auto-Summary in RIPv2

the results of using

RIPv2 are different,

allowing both CIDR and

VLSM to be used in the

network

RIPv1

0 7|8 15 |16 23 | 24 31 Bit

Address Family Identifier (2 = IP) Must Be Zero

IP Address (Network Address) Route

Entry 4 Must Be Zero

Must Be Zero

Metric (Hops) Multiple Route Entries, Up to a Maximum of 25

Enabling and Verifying RIPv2

RIPv1

RIPv2 is defined in Bà

RFC 1723 non Eany beerEsIE) =

RIPv2 message IP Address (Network Address)

format is the subnet em 7 Must Be Zero

mask field that allows Must Be Zero

included in the RIP Multiple Route Entries, Up to a Maximum of 25

the subnet mask of IP Address (Network Address)

Route

or the classful mask

Enabling and Verifying RIPv2

R2# show ip protocols

<output omitted>

Default version control: send version 1, receive any version

Default RIPv1: When configuring RIP

Router only sends RIPv1 messages, It can process both RIPv1 and

RIPv2 messages

Ignore the RIPv2 fields in the route entry

@® RIPv2 will ignore RIPv1 updates

@ FYI only: The interface commands ip rip sendandip rip receive

can be used to force compatibility between different versions

Enabling and Verifying RIPv2

® version 2 command is used to modify RIP to use Version 2

@ This command should be configured on all routers in the routing

domain.

Enabling and Verifying RIPv2

R2# show ip protocols

4 1 hd

Routing Protocol is “rip

Sending updates every 30 seconds, next due in 1 seconds

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

Outgoing update filter list for all interfaces is

Incoming update filter list for all interfaces is

Redistributing: static, rip

Default version control: send version 2, receive version 2

Automatic network summarization is in effect

S1

Restoring RIP to Version 1

@ Default behavior of RIPv1 can be restored by using either the

(slightly different behaviors in sending and receiving):

version 1 command

no version command

@ lf done, should be configured on all routers

92