Tài liệu Routing Principles and IOS Implementation Lab Scenario doc

Berkowitz Objective A Reality Check Router Configurations PARSLEY's Configuration: THYME's Configuration: SAGE's Configuration: ROSEMARY's Configuration: First Pass Router Configu

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Date of Issue: 11-01-1999

Routing Principles and IOS

Implementation

Lab Scenario

by Howard C Berkowitz

Objective

A Reality Check

Router Configurations

PARSLEY's Configuration:

THYME's Configuration:

SAGE's Configuration:

ROSEMARY's Configuration:

First Pass

Router Configurations

PARSLEY's Configuration:

THYME's Configuration:

SAGE's Configuration:

ROSEMARY's Configuration:

Analysis

TIP

The Distance command

Objective

The existing configuration runs IGRP Convert the network to run OSPF without using redistribution Run OSPF and IGRP in parallel at first, continuing the use of IGRP as the active routing protocol, until you verify OSPF operation

Figure 1 shows the initial physical configuration and addressing of the routers

Figure 1

A Reality Check

Can you ping and traceroute to all interfaces, including the loopbacks? Why? Why not?

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Router Configurations

These configurations work with IGRP

PARSLEY's Configuration:

parsley#s ru

Building configuration

Current configuration:

!

version 11.0

service udp-small-servers

service tcp-small-servers

!

hostname parsley

!

enable password pass

!

ip subnet-zero

!

interface Loopback0

ip address 192.168.254.254 255.255.255.0

!

interface Ethernet0

ip address 192.168.1.1 255.255.255.0

!

interface Ethernet1

no ip address

shutdown

!

interface Serial0

ip address 192.168.3.1 255.255.255.252

no fair-queue

!

interface Serial1

no ip address

shutdown

!

interface TokenRing1

no ip address

shutdown

!

ip address 192.168.2.1 255.255.255.0

ring-speed 16

!

router igrp 1

network 192.168.1.0

network 192.168.2.0

network 192.168.3.0

!

ip host thyme 192.168.1.2

ip host sage 192.168.1.3

ip host rosemary 192.168.1.4

!

line con 0

exec-timeout 0 0

line aux 0

transport input all

line vty 0 4

no login

!

end

parsley#

THYME's Configuration:

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thyme#s ru

!

version 11.0

!

hostname thyme

!

ip subnet-zero

!

interface Loopback0

ip address 192.168.253.253 255.255.255.0

!

interface Ethernet0

ip address 192.168.1.2 255.255.255.0

!

interface Ethernet1

no ip address

shutdown

!

interface Ethernet2

no ip address

shutdown

!

interface Ethernet3

no ip address

shutdown

!

interface Serial0

ip address 192.168.3.2 255.255.255.252

no fair-queue

!

interface Serial1

ip address 192.168.3.5 255.255.255.252

!

interface Serial2

no ip address

shutdown

!

interface Serial3

no ip address

shutdown

!

no ip address

shutdown

!

ip address 192.168.2.2 255.255.255.0

ring-speed 16

!

router igrp 1

network 192.168.1.0

network 192.168.2.0

network 192.168.3.0

!

ip host parsley 192.168.1.1

!

line con 0

line aux 0

transport input all

line vty 0 4

no login

!

end

thyme#

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SAGE's Configuration:

sage#s ru

!

version 11.0

!

hostname sage

!

interface Loopback0

ip address 192.168.252.252 255.255.255.0

!

interface Ethernet0

ip address 192.168.1.3 255.255.255.0

!

interface Ethernet1

no ip address

shutdown

!

interface Serial0

ip address 192.168.3.6 255.255.255.252

no fair-queue

!

interface Serial1

no ip address

shutdown

!

no ip address

shutdown

!

ip address 192.168.2.3 255.255.255.0

ring-speed 16

!

router igrp 1

network 192.168.1.0

network 192.168.2.0

!

line con 0

line aux 0

transport input all

line vty 0 4

no login

!

end

sage#

ROSEMARY's Configuration:

rosemary#s ru

!

version 11.0

!

hostname rosemary

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!

interface Loopback0

ip address 192.168.251.251 255.255.255.0

!

interface Ethernet0

ip address 192.168.1.4 255.255.255.0

!

interface Ethernet1

no ip address

shutdown

!

interface Serial0

no ip address

shutdown

no fair-queue

!

interface Serial1

no ip address

shutdown

!

no ip address

shutdown

!

ip address 192.168.2.4 255.255.255.0

ring-speed 16

!

router igrp 1

network 192.168.1.0

network 192.168.2.0

!

line con 0

exec-timeout 0 0

line aux 0

transport input all

line vty 0 4

no login

!

end

First Pass

Here's a first attempt at the solution, improved by adding a more efficient addressing structure Does it meet the requirements of the scenario? (see "First Pass Analysis" below.)

Router Configurations

PARSLEY's Configuration:

parsley#s ru

!

version 11.0

!

hostname parsley

!

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!

ip subnet-zero

!

interface Loopback0

ip address 192.168.254.254 255.255.255.0

!

interface Ethernet0

ip address 192.168.1.1 255.255.255.0

!

interface Ethernet1

no ip address

shutdown

!

interface Serial0

ip address 192.168.3.1 255.255.255.252

no fair-queue

!

interface Serial1

no ip address

shutdown

!

no ip address

shutdown

!

ip address 192.168.2.1 255.255.255.0

ring-speed 16

!

router ospf 1

network 192.168.1.1 0.0.0.0 area 0.0.0.1

network 192.168.2.1 0.0.0.0 area 0.0.0.1

network 192.168.3.1 0.0.0.0 area 0.0.0.1

network 192.168.254.254 0.0.0.0 area 0.0.0.1

!

router igrp 1

network 192.168.1.0

network 192.168.2.0

network 192.168.3.0

!

line con 0

exec-timeout 0 0

line aux 0

transport input all

line vty 0 4

no login

!

end

parsley#

THYME's Configuration:

thyme#s ru

!

version 11.0

!

hostname thyme

!

ip subnet-zero

!

interface Loopback0

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ip address 192.168.253.253 255.255.255.0

!

interface Ethernet0

ip address 192.168.1.2 255.255.255.0

!

interface Ethernet1

no ip address

shutdown

!

interface Ethernet2

no ip address

shutdown

!

interface Ethernet3

no ip address

shutdown

!

interface Serial0

ip address 192.168.3.2 255.255.255.252

no fair-queue

!

interface Serial1

ip address 192.168.3.5 255.255.255.252

!

interface Serial2

no ip address

shutdown

!

interface Serial3

no ip address

shutdown

!

no ip address

shutdown

!

ip address 192.168.2.2 255.255.255.0

ring-speed 16

!

router ospf 1

network 192.168.1.2 0.0.0.0 area 0.0.0.1

network 192.168.2.2 0.0.0.0 area 0.0.0.1

network 192.168.3.2 0.0.0.0 area 0.0.0.1

network 192.168.3.5 0.0.0.0 area 0.0.0.1

network 192.168.253.253 0.0.0.0 area 0.0.0.1

!

router igrp 1

network 192.168.1.0

network 192.168.2.0

network 192.168.3.0

!

line con 0

line aux 0

transport input all

line vty 0 4

no login

!

end

thyme#

SAGE's Configuration:

sage#s ru

!

version 11.0

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!

hostname sage

!

interface Loopback0

ip address 192.168.252.252 255.255.255.0

!

interface Ethernet0

ip address 192.168.1.3 255.255.255.0

!

interface Ethernet1

no ip address

shutdown

!

interface Serial0

ip address 192.168.3.6 255.255.255.252

no fair-queue

!

interface Serial1

no ip address

shutdown

!

no ip address

shutdown

!

ip address 192.168.2.3 255.255.255.0

ring-speed 16

!

router ospf 1

network 192.168.1.3 0.0.0.0 area 0.0.0.1

network 192.168.2.3 0.0.0.0 area 0.0.0.1

network 192.168.3.6 0.0.0.0 area 0.0.0.1

network 192.168.252.252 0.0.0.0 area 0.0.0.1

!

router igrp 1

network 192.168.1.0

network 192.168.2.0

!

line con 0

line aux 0

transport input all

line vty 0 4

no login

!

end

sage#

ROSEMARY's Configuration:

rosemary#s ru

!

version 11.0

!

hostname rosemary

!

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interface Loopback0

ip address 192.168.251.251 255.255.255.0

!

interface Ethernet0

ip address 192.168.1.4 255.255.255.0

!

interface Ethernet1

no ip address

shutdown

!

interface Serial0

no ip address

shutdown

no fair-queue

!

interface Serial1

no ip address

shutdown

!

no ip address

shutdown

!

ip address 192.168.2.4 255.255.255.0

ring-speed 16

!

router ospf 1

network 192.168.1.4 0.0.0.0 area 0.0.0.1

network 192.168.2.4 0.0.0.0 area 0.0.0.1

network 192.168.251.251 0.0.0.0 area 0.0.0.1

!

router igrp 1

network 192.168.1.0

network 192.168.2.0

!

line con 0

exec-timeout 0 0

line aux 0

transport input all

line vty 0 4

no login

!

end

Analysis

These configurations do not meet the requirements You have a mixture of IGRP and OSPF routes in the active routing table, which was not the goal The goal was to keep IGRP running, verify OSPF was collecting the proper topology, and only then convert to OSPF

What is wrong?

This space left blank so that you don't peek at the

answer! ;-)

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The reconfiguration was too ambitious It attempted simultaneously to introduce a new routing protocol and a new addressing scheme

See the Tutorial "Routing Principles and IOS Implementation Considerations" for a discussion of how routes are chosen for routing table installation The person writing this first configuration forgot that prefix length the number of one bits in the subnet mask is considered before administrative distance

While he correctly observed that OSPF's administrative distance is higher (i.e., less preferred) than IGRP's, he forgot that the VLSM subnets introduced into the network were more specific, and thus preferable, to any IGRP route

The proper approach to this problem is to change one thing at a

time:

• Add the OSPF routing protocol

• Verify operation

• Add distance commands to make OSPF the preferred protocol

over IGRP

• Change the addressing to VLSM

• Add summarization, stubby areas, and other OSPF

enhancements (not a requirement for this specific scenario)

The Distance command

Cisco uses administrative distance to decide which source is "most

believable" about a route to a certain destination Administrative

distance breaks ties between routes of the same specificity the

same prefix length (i.e., number of one bits in the subnet mask)

to a given destination

In the accompanying Tutorial, you will see the default

administrative distance that the IOS assigns to each source of

routing information You can override these defaults with the

distance subcommand, which you code underneath a router

major command

TIP

When upgrading both the dynamic routing protocol and the addressing, upgrade the routing protocol first, verify operation, and only then renumber Keep the network stable during conversion, changing one thing at a time

The Bay RS operating system, which is the equivalent of IOS for Nortel routers and is also the base of Microsoft RRAS, contains a default for OSPF routes that differs from Cisco's but can be quite useful

Since Bay does not support proprietary IGRP, they assumed that any conversions would be from RIP to OSPF In Bay RS, the OSPF interface costs defaults to 1, rather than the 108/bandwidth used by most vendors, including Cisco

By setting the default to 1, the sum of costs along any path becomes the hop count At least inside areas, OSPF will select the same paths as would RIP, which simplifies

verification that the new protocol is working in the same way as the old

True, summarization at area boundaries, and

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The simplest form of distance changes the administrative distance

of all routing information received from a given source:

Router rip

Redistribute igrp 1

Distance 130

The lines above will assign an administrative distance of 130 to all

IGRP routes learned by RIP RIP's default administrative distance

is 120 By overriding the administrative distance, you make the

routes redistributed into RIP less desirable than those routes originated in RIP

Does this form of the distance command fit our scenario, which specifies that you should not use redistribution?

Router igrp 1

Network 172.17.0.0

Distance 120 172.17.1.1 0.0.0.0 1

Access-list 1 permit 172.16.0.0 0.0.255.255

The second form, shown above, is more appropriate for this scenario In the example, IGRP sets the distance to 120 for all routes received from the advertising router (172.16.2.1) that match access-list 1

In the distance command, the address and wildcard mask in the distance statement refer to the address of the

advertising router, not the route itself When using the distance statement with OSPF, the address and wildcard mask will refer to the router id of the originating router For this reason, you should use 0.0.0.0 255.255.255.255 to specify any router speaking OSPF

So, to make OSPF routes learned to be less preferred to those learned from IGRP, you would code:

Router ospf 1

Network 172.17.0.0

Distance 120 0.0.0.0 255.255.255.255 1

Access-list 1 permit 0.0.0.0 255.255.255.255

[IE-RPIO-LS1-F03]

[1999102108] outputWP() End: 1999-10-21 11:51:00

True, summarization at area boundaries, and the use of stubby areas with multiple area border routers, may change the routing with respect to RIP What does that suggest? That, perhaps, summarization and stubby areas should be added once the basic OSPF is working? After all, the existing network is working, to some extent, without them

Bay does recommend changing the inteface costs to 108/bandwidth once the conversion is complete Summarization and stub areas can

be added after the costs are changed

Tiêu đề	Routing Principles And Ios Implementation Lab Scenario
Tác giả	Howard C. Berkowitz
Trường học	CertificationZone
Thể loại	Tài liệu
Năm xuất bản	1999

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Số trang	11
Dung lượng	43,84 KB