BSCI

Building Scalable Cisco
Internetworks
Version 1.2

Student Guide

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ROUTING PRINCIPLES 2-1
Overview 2-1
Objectives 2-2
Classful Routing Protocol Overview 2-3
Classless Routing Overview 2-6
Distance Vector Operation 2-9
Link-State Operation 2-10
Written Exercise: Comparing Routing Protocols 2-29
Objective 2-29
Task 2-29
Completion Criteria 2-30
Summary 2-31
Review Questions 2-32
EXTENDING IP ADDRESSES 3-1
Overview 3-1
Objectives 3-2
IP Addressing Issues 3-3
IP Addressing Solutions 3-4
Hierarchical Addressing 3-9
VLSMs 3-11
Written Exercise 1: Calculating VLSMs 3-14
Objective 3-14
Task 3-14
Completion Criteria 3-14
Route Summarization 3-15
Written Exercise 2: Using Route Summarization 3-25
Objective 3-25
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vi Building Scalable Cisco Internetworking Copyright  2001, Cisco Systems, Inc.
Task 1 3-25

Written Exercise: OSPF Operation 5-34
Objective 5-34
Task 5-34
Completion Criteria 5-35
Configuring OSPF in a Single Area 5-36
Verifying OSPF Operation 5-48
Summary 5-57
Summary (cont.) 5-58
Review Questions 5-59
INTERCONNECTING MULTIPLE OSPF AREAS 6-1
Overview 6-1
Objectives 6-2
Objectives (cont.) 6-3
Copyright  2001, Cisco Systems, Inc. Building Scalable Cisco Internetworking vii
Creating Multiple OSPF Areas 6-4
Routing Table Results with Different Areas 6-14
OSPF Operation Across Multiple Areas 6-15
Virtual Links Overview 6-18
Written Exercise: OSPF Operation Across Multiple Areas 6-20
Objective 6-20
Task 6-20
Completion Criteria 6-21
Using and Configuring OSPF Multiarea Components 6-22
Verifying OSPF Operation 6-40
Summary 6-42
Summary (cont.) 6-43
Review Questions 6-44
CONFIGURING IS-IS PROTOCOL 7-1
Overview 7-1
Objectives 7-2

When Not to Use BGP 9-10
BGP Terminology 9-14
BGP Operation 9-38
Written Exercise: BGP Terminology and Operation 9-44
Objectives 9-44
Task 9-44
Completion Criteria 9-45
Configuring BGP 9-46
Verifying BGP 9-57
Summary 9-62
Review Questions 9-64
IMPLEMENTING BGP IN SCALABLE NETWORKS 10-1
Overview 10-1
Objectives 10-2
Objectives (cont.) 10-3
Scalability Problems with IBGP 10-4
Route Reflectors 10-7
Policy Control 10-17
Written Exercise: BGP Route Reflectors and Policy Control 10-28
Objectives 10-28
Task 10-28
Completion Criteria 10-29
Multihoming 10-30
Redistribution with IGPs 10-45
Summary 10-52
Summary (cont.) 10-53
Review Questions 10-54
JOB AIDS AND SUPPLEMENTS A-1
Overview A-1
Extending IP Addresses A-2

Answers to Written Exercise: OSPF Operation C-8
Answers to Review Questions C-9
Chapter 6 Exercises C-10
Answers to Written Exercise: OSPF Operation Across Multiple Areas C-10
Answers to Review Questions C-11
Chapter 7 C-13
Answers To Review Questions 13
Answers to Written Exercise: Redistribution and Controlling Routing Update
Traffic C-15
Answers To Review Questions C-16
Chapter 9 Exercises C-18
Answers to Written Exercise: BGP Terminology and Operation C-18
Answers to Review Questions C-19
Chapter 10 Exercises C-21
Answers to Written Exercise: BGP Route Reflectors and Policy Control C-21
Answers to Review Questions C-22
Appendix A Exercises C-23
Answers to Extending IP Addressing Written Exercise: Calculating Subnet
Masks C-23
Answers to IP Access Lists Written Exercise: IP Extended Access Lists C-24
Answers to Review Questions C-24
Laboratory Exercises Written Questions C-25
Laboratory Exercise 1: Configuring EIGRP C-25
Laboratory Exercise 2: Configuring OSPF for a Single Area C-25
Laboratory Exercise 3: Configuring OSPF for a Single Area in an NBMA
Environment C-25
Laboratory Exercise 4: Configuring a Multiarea OSPF Network C-26
Laboratory Exercise 5: Configuring a Multiarea IS-IS Network C-26
Laboratory Exercise 6: Configuring Policy-Based Routing C-26
Laboratory Exercise 7: Configuring Route Redistribution between OSPF and

Environment D-18
Objectives D-18
Visual Objective D-19
Command List D-20
Setup D-20
Scenario D-20
Task 1: Creating the Frame Relay Switch D-21
Task 2: Enabling OSPF Over an NBMA Network Using a Main Interface D-22
Task 3: Enabling OSPF Over an NBMA Network Using a Point-to-Point
Subinterface D-23
Completion Criteria D-23
Student Notes D-24
Laboratory Exercise 4: Configuring a Multiarea OSPF Network D-25
Objectives D-25
Visual Objective D-26
Command List D-27
Setup D-28
Scenario D-29
Task 1: Enabling OSPF with Multiple Areas and Area Summarization D-29
Task 2: Enabling OSPF Stub Area D-31
Task 3: Enabling an OSPF Totally Stubby Area D-31
Task 4: Enabling OSPF Not-So-Stubby Area (Optional) D-32
Task 5: Enabling an OSPF Virtual Link to Support an OSPF Area not
Connected to Area 0 (Optional) D-35
Completion Criteria D-37
Student Notes D-38
Laboratory Exercise 5: Configuring a Multiarea IS-IS Network D-39
Objectives D-39
Visual Objective D-40
Command List D-41

Task 2: Enabling EIGRP Between pxr1 (S2) and pxr3 (S0) D-58
Task 3: Enabling Route Redistribution Between OSPF and EIGRP D-58
Task 4: Enabling Route Redistribution from EIGRP
to OSPF with Filtering D-59
Completion Criteria D-60
Student Notes D-61
Laboratory Exercise 8: Configuring BGP D-62
Objectives D-62
Visual Objective D-63
Command List D-63
Setup D-65
Scenario D-65
Task 1: Enabling EBGP D-66
Task 2: Enabling Full-Mesh IBGP Within Your Pod (AS) D-68
Completion Criteria D-70
Student Notes D-71
Laboratory Exercise 9: Configuring BGP Route Reflectors and Prefix-List
Filtering D-72
Objectives D-72
Visual Objective D-72
Command List D-73
Setup D-73
Scenario D-73
Task 1: Enabling pxr1 to be the Route Reflector D-74
Task 2: Enabling Inbound Prefix-List D-76
Completion Criteria D-76
Student Notes D-77
Laboratory Exercise 10: Configuring Multi-homed BGP D-78
Objectives D-78
Visual Objective D-79

7 1
Configuring IS-IS Protocol 2
Overview 3
This lesson provides an overview of Intermediate System-to-Intermediate System (IS-IS) 4
technology, and its structures and protocols, as well as basic configuration examples. The lesson 5
begins with Open System Interconnection (OSI) routing and then focuses on Integrated IS-IS as 6
a version that supports IP networks. Basic IS-IS and Integrated IS-IS router configuration 7
commands, examples, and some troubleshooting guidelines are presented at the end of the 8
lesson. The major part of this lesson is dedicated to an explanation of IS-IS concepts and 9
capabilities, including hierarchy and addressing of OSI-based networks. 10
Outline 11
The lesson includes these sections: 12
n Objectives 13
n Introduction to OSI Protocols and IS-IS Routing 14
n Operation of IS-IS 15

Copyright  2001, Cisco Systems, Inc. Configuring IS-IS Protocol 7-3
Objectives (cont.) 29
Insert Slide here.
n Describe the concept of establishing adjacencies 30
n Describe the concepts of routing traffic transport and database synchronization 31
n Explain the basic principles of area routing 32
n Explain IS-IS nonbroadcast multiaccess (NBMA) network modeling solutions in switched 33
WAN networks 34
n Identify the steps to configure Cisco routers for proper Integrated IS-IS operation, given an 35
addressing scheme and other laboratory parameters 36
n Identify verification methods that ensure proper operation of Integrated IS-IS on Cisco 37
routers 38
© 2001, Cisco Systems, Inc. BSCI v1.2 — 7-3
Objectives (cont.)
Objectives (cont.)
• Describe the concept of establishing adjacencies
• Describe the concepts of routing traffic transport and
database synchronization
• Explain the basic principles of area routing
• Explain IS-IS NBMA (non-broadcast multi-access
network) modeling solutions in switched WAN
networks
• Given an addressing scheme and other laboratory
parameters, identify the steps to configure Cisco
routers for proper Integrated IS-IS operation
• Identify verification methods which ensure proper
operation of Integrated IS-IS on Cisco routers
7-4 Building Scalable Cisco Internetworks (BSCI) v1.2 Copyright  2001, Cisco Systems, Inc.
Introduction to OSI Protocols and IS-IS 39
Routing 40

OSI network-layer addressing is implemented by using two types of hierarchical addresses: 57
network service access point (NSAP) addresses and network-entity titles. An NSAP is a 58
conceptual point on the boundary between the network and the transport layers. The NSAP is 59
the location at which OSI network services are provided to the transport layer. Each transport-60
layer entity is assigned a single NSAP, which is individually addressed in an OSI internetwork 61
using NSAP addresses. 62
The OSI protocol suite specifies two routing protocols at the network layer: End System-to-63
Intermediate System (ES-IS) and Intermediate System-to-Intermediate System (IS-IS). In 64
addition, the OSI suite implements two types of network services: connectionless service and 65
connection-oriented service. 66
© 2001, Cisco Systems, Inc. BSCI v1.2 — 7-6
OSI Protocols (cont.)OSI Protocols (cont.)
The OSI protocol suite supports:
• Numerous standard protocols at each layer of
the OSI reference model
• OSI network-layer
hierarchical addressing
• Two routing protocols at the
network layer
7-6 Building Scalable Cisco Internetworks (BSCI) v1.2 Copyright  2001, Cisco Systems, Inc.
Insert Slide here.
In an OSI network four significant architectural entities exist: hosts, areas, a backbone, and a 67
domain. A domain is any portion of an OSI network that is under a common administrative 68
authority. Within any OSI domain, one or more areas can be defined. An area is a logical entity; 69
it is formed by a set of contiguous routers and the data links that connect them. All routers in 70
the same area exchange information about all the hosts that they can reach. The areas are 71
connected to form a backbone. All routers on the backbone know how to reach all areas. The 72
term “end system” (ES) refers to any nonrouting host or node; “intermediate system” (IS) 73
refers to a router. These terms are the basis for the OSI ES-IS and IS-IS protocols. 74
© 2001, Cisco Systems, Inc. BSCI v1.2 — 7-7

convey data at the network layer. CLNP is the OSI equivalent of IP. 84
© 2001, Cisco Systems, Inc. BSCI v1.2 — 7-9
OSI Network Services—
What to Route in OSI Environment?
OSI Network Services—
What to Route in OSI Environment?
Two types of OSI network-layer services
are available to the OSI transport layer:
• Connectionless Network Service (CLNS)
–CLNS performs datagram transport
• Connection-Mode Network Service (CMNS)
–CMNS requires explicit establishment
of paths between communicating transport-
layer entities
Copyright  2001, Cisco Systems, Inc. Configuring IS-IS Protocol 7-9
Insert Slide here.
CONP is based on the X.25 Packet-Layer Protocol (PLP) and is described in the ISO 8208 85
standard “X.25 Packet-Layer Protocol for DTE.” 86
CONP provides the interface between CMNS and upper layers. It is a network-layer service 87
that acts as the interface between the transport layer and CMNS and is described in the ISO 88
8878 standard. CMNS functions include connection setup, maintenance, and termination; it also 89
provides a mechanism for requesting a specific QoS. 90
© 2001, Cisco Systems, Inc. BSCI v1.2— 7-10
OSI Network Services—
Connection-Oriented Mode
OSI Network Services—
Connection-Oriented Mode
CMNS/CONP:
• CONP is an OSI network-layer protocol that
carries upper-layer data and error indications

Insert Slide here.
The OSI protocol suite includes several routing protocols and one router discovery protocol (ES-98
IS, an analog to Address Resolution Protocol [ARP] in IP). Although not explicitly a routing 99
protocol, ES-IS is included in this lesson because it is commonly used with routing protocols to 100
provide end-to-end data movement through an internetwork. 101
To simplify router design and operation, OSI distinguishes between level-1, level-2, and level-3 102
routing. Level-1 ISs communicate with other level-1 ISs in the same area. Level-2 ISs route 103
between level-1 areas and form an intradomain routing backbone. Level-3 routing is done 104
between separate domains. 105
Hierarchical routing simplifies backbone design, because level-1 ISs only need to know how to 106
get to the nearest level-2 IS. 107
© 2001, Cisco Systems, Inc. BSCI v1.2— 7-12
OSI Network Services—Routing
Protocols
OSI Network Services—Routing
Protocols
ISO has developed standards for two
types of protocols:
• ES-IS dicovery protocols: “routing” between
End Systems and Intermediate Systems
referred as level-0 “routing”
• IS-IS routing protocols: hierarchical
(level-1, level-2 and level-3) routing between
Intermediate Systems
7-12 Building Scalable Cisco Internetworks (BSCI) v1.2 Copyright  2001, Cisco Systems, Inc.
Insert Slide here.
Each ES lives in a particular area. OSI routing begins when the ESs discover the nearest IS by 108
listening to Intermediate System Hello (ISH) packets. When an ES wants to send a packet to 109
another ES, it sends the packet to one of the ISs on its directly attached network (level-0 110
routing). The router then looks up the destination address and forwards the packet along the 111

within the same area
Level-2 routing between different
areas within the same domain
Level-2 routing between different
areas within the same domain
Level-3 routing between separate domains
Level-3 routing between separate domains
Copyright  2001, Cisco Systems, Inc. Configuring IS-IS Protocol 7-13
Insert Slide here.
For routing in the ISO CLNS/CLNP environment, Cisco routers support these protocols: 123
n IS-IS: Routers usually operate as ISs and can exchange reachability information with other 124
ISs using the IS-IS protocol. As an IS, a Cisco router can operate at level 1 only, at level 2 125
only, or at both levels. In the last case, the router can advertise itself at level 1 as an exit 126
point from the area. Integrated IS-IS allows the IS-IS protocol to propagate routing 127
information for other protocols as well as, or instead of, CLNS. Specifically, IS-IS can route 128
CLNS, IP, or both (“dual” mode). 129
n ISO-IGRP: Cisco routers have available a proprietary routing protocol for CLNS. ISO-130
IGRP is, as its name suggests, based on Cisco’s Interior Gateway Routing Protocol (IGRP). 131
It uses distance vector technology to propagate routing information. As such, it shares some 132
of the limitations of its IP counterpart, including long convergence times (due to periodic 133
updates and long invalid-times and holdtimes). 134
n Static CLNS routes: As with IP, static CLNS routes can be created. 135
© 2001, Cisco Systems, Inc. BSCI v1.2— 7-14
OSI Network Services—IS-IS RoutingOSI Network Services—IS-IS Routing
Intermediate System to Intermediate
System (IS-IS) is a dynamic link-state
routing protocol in ISO CLNS environment
for routing CLNP
• Link-state routing protocol in the OSI stack
Alternative to IS-IS protocols is deploying