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CISCO QoS
ADMINISTERING
“This book provides comprehensive, in-depth explanations
and configurations necessary to implement QoS in today's
advanced, multiservice Cisco networks.”
—Ralph Troupe, President and CEO, Callisma
IP NETWORKS
®
IN
TECHNICAL EDITOR: Michael E. Flannagan, CCNA, CCDA
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v
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vi
From Michael E. Flannagan,
Technical Editor
A world of thanks to the Cisco RTP Routing Protocols Team for an unbelievable
amount of knowledge, experience, assistance, and fun…you guys are the best! Thanks
to Matt Carling (Cisco Systems, Australia) for his assistance with our MPLS chapter.
Special thanks to Shannon Brown (Cisco Systems,TAC) for her knowledge and
especially her patience back in the days when I could hardly spell “router.” And, of
course, I’ll be disowned if I don’t say…Hi mom!
110_QoS_FM 2/13/01 4:42 PM Page vi
vii
From Global Knowledge
At Global Knowledge we strive to support the multiplicity of learning styles
required by our students to achieve success as technical professionals. As the
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viii
Technical Editor
110_QoS_FM 2/13/01 4:42 PM Page viii
ix
Contributors
Benoit Durand (CCIE #5754, CCNA, CCDA, CCNP, CCDP) is the
Midwest Region Network Engineer for Tivoli Systems (www.tivoli.com)
located in Indianapolis, IN. Ben designs and integrates high-end network
solutions for Tivoli’s worldwide operations while maintaining his own
Cisco-powered network in Indianapolis. He has over 10 years of net-
working engineering experience in a wide range of environments. Prior
to working at Tivoli, Ben worked on many high-profile military projects
for the Canadian Air Force, deploying wide-area network solutions to
peacekeeping forces in Kuwait,Yugoslavia, and other international loca-
tions. His latest projects involve Voice-over-ATM,Virtual Private Network
solutions, and Wide-Area Network switching. Ben lives with his wife Dr.
Christy Snider in Kingston, GA.
Ron Fuller (CCIE #5851, CCNP-ATM, CCNP-Voice, CCNP-Security,
CCDP, MCNE) is a Senior Systems Engineer with 3X Corporation. He
currently provides network design and implementation services to 3X
Corporation clients in the Eastern United States. His specialties include
Cisco LAN/WAN design, security consultation, and Novell network
design. He has held senior engineer positions for two other network con-
sulting companies in the past nine years. Ron also contributed to Syngress’
Building Cisco Remote Access Networks (1-928994-13-X). He currently

Paul Salas (CCNA, MCT, MCSE, Network+) is a Senior Network
Engineer for Fleet Mortgage Corporation. Paul designs and manages
Fleet’s internetwork infrastructure, which consists of a wide variety of
networking equipment from an assortment of vendors. He currently is
involved in implementing a high-end Web network solution. He is also a
part-time technical instructor for Microstaff Corporation where he
delivers Microsoft Official Curriculum for the Windows 2000 track. Paul
lives in Columbia, SC with his family. He would like to dedicate his writ-
ings to his wife, Margaret, for tolerating his “hair on fire” work pace and
to his two children, Michael and Allison, Mountains are conquered one step at
a time.
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xi
Jeff Corcoran (CCNA, MCSE, CNE) is a Senior Network Consultant
for Siemens Enterprise Networks, Inc. where he is a network planner in
the Ford Motor Company Advanced Network Technologies group. He is
responsible for global network planning and testing of emerging network
technologies and their application to the Ford Intranet. He has a special
focus on VoIP, QoS, high availability architectures, and multicast. Jeff holds
a Bachelors of Science in Physics and Applied Mathematics from the
University of Toledo. He lives in Dearborn, MI.
Lisa Giebelhaus (CCNA) is a Senior Consultant with Callisma. She has
been in the Telecommunications field for eight years. Her main focus has
been designing, implementing, and managing projects for large-scale enter-
prise networks. Prior to joining Callisma, Lisa was a Senior Consultant for
Lucent NetworkCare Professional Services (formerly INS) in Detroit, MI.
She graduated from Michigan State University with a Bachelor of Science
degree in Engineering Arts. She lives in Royal Oak, MI.
Richard Hamilton is a Senior Consultant with Callisma. He is currently
responsible for leading engineering teams in the design and implementa-

RIPv1 11
IGRP 13
Variable-Length Subnet Mask (VLSM) Review 17
Why Do We Need VLSM? 19
Common Uses for Subnetting 20
Standard Access Control Lists (ACLs) 21
Filtering Traffic 24
Configuration Examples 25
Extended Access Control Lists (ACLs) 25
Benefits of Extended ACLs 30
Common Ports Used with Extended ACLs 30
Configuration Examples 32
Network Address Translation (NAT) 35
Controlling NAT with ACLs 39
Dynamic versus Static Translations 39
Configuration Example 40
Route Maps 40
Where to Use Route Maps 41
Controlling Traffic with Route Maps 41
Configuration Example 41
Summary 43
FAQs 44
Chapter 2 EIGRP A Detailed Guide 47
Introduction 48
Reviewing Basic Concepts of IGRP 48
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xiv Contents
How Does EIGRP Work? 50
Using Distance Vectors for Path Selection 50
Defining the Four Basic Components of EIGRP 57

Understanding Congestion Management 129
Defining General Queuing Concepts 130
Leaky Bucket 131
Tail Drop 132
Token Bucket 133
First In First Out Queuing 134
Fair Queuing 136
Priority Queuing 138
Custom Queuing 139
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Contents xv
Understanding Congestion Avoidance 141
Congestion Avoidance in Action 142
Pros and Cons of Congestion Avoidance 142
Introducing Policing and Traffic Shaping 143
Traffic Shaping 144
Generic Traffic Shaping 145
Frame Relay Traffic Shaping 145
Summary 145
FAQs 146
Chapter 4 Traffic Classification Overview 147
Introduction 148
Introducing Type of Services (ToS) 148
ToS Service Profile 150
Defining the Seven Levels of IP Precedence 151
Explaining Integrated Services 152
Defining the Parameters of QoS 154
Admission Requirements 155
Resource Reservation Requirements 156
Packet Classification 156

Configuring Distributed CAR (DCAR) 188
Marking and Transmitting Web Traffic 188
Remarking the Precedence Bit
and Transmitting Web Traffic 189
Marking and Transmitting Multilevels of CAR 190
Marking and Rate Limiting ISPs 191
Rate Limiting by Access List 193
Using CAR to Match and Limit by MAC Address 194
Monitoring CAR 196
Configuring Cisco Express Forwarding 196
Enabling CEF 197
Monitoring CEF 198
Troubleshooting Cisco Express Forwarding
Caveats and Bugs 200
Configuring Basic Network-based Application
Recognition (NBAR) 201
Creating an NABR Class Map 202
Creating a Policy Map 203
Applying the Policy Map to an Interface 203
Configuring Complex NBAR 204
Integrating NBAR with Class-based Weighted Fair Queuing 206
Creating a Class Map to Identify NBAR 207
Configuring Class Policy in the Policy Map 207
Attaching the Policy to an Interface 208
Configuring NBAR with Random Early Detection 209
Configuring System Network Architecture Type of Service 211
Mapping SNA CoS to IP ToS 211
Prioritizing SNA Traffic 212
Summary 213
FAQs 215

Chapter 7 Configuring Queuing
and Congestion Avoidance 239
Introduction 240
Configuring FIFO Queuing 240
Enabling FIFO 240
Verifying FIFO Operations 242
FIFO with RED 243
Configuring Priority Queuing 244
Enabling Priority Queuing 244
A Closer Look at the Protocol Classification 245
Applying Your Priority List to an Interface 247
Configuring the Queue Limits 247
Verifying Your Configuration 248
Troubleshooting Priority Queuing 250
Configuring Custom Queuing 252
Enabling Custom Queuing 252
Adjusting Byte Counts and Queue Sizes 254
Applying Your Configuration to an Interface 254
Verifying Your Configuration 255
Troubleshooting Custom Queuing 257
Configuring Weighted Fair Queuing 259
Enabling Weighted Fair Queuing 259
Verifying Your Configuration 260
Troubleshooting Weighted Fair Queuing 262
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xviii Contents
Configuring Random Early Detection 263
Enabling Random Early Detection 263
RED with Other Queuing Mechanisms 264
Verifying Your Configuration 266

WRED Algorithm 297
Why Do I Need WRED on My Network? 298
Using Generic Traffic Shaping and Frame
Relay Traffic Shaping 299
Token Bucket 299
How Does GTS Work? 301
Why Do I Need GTS on My Network? 301
How Does FRTS Work? 303
Why Do I Need FRTS on My Network? 305
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Contents xix
Running in Distributed Mode 307
Features Supported in Distributed Mode 307
IOS Versions 308
Operational Differences 308
Restrictions 308
Using Link Fragmentation and Interleaving 309
How Does LFI Work? 311
LFI with Multilink Point-to-Point Protocol 312
How Can This Be Useful on My Network? 313
Understanding RTP Header Compression 313
How Does RTP Header Compression Work? 314
When Would I Need RTP Header Compression? 315
Summary 315
FAQs 318
Chapter 9 Configuring Advanced QoS 321
Introduction 322
Enabling, Verifying, and Troubleshooting
Resource Reservation Protocol (RSVP) 322
Enabling RSVP 324

Configuring Traffic Shaping Parameters 354
Configuring Queuing for the VC 356
Applying Map Class to the Frame Relay Interface 357
Verifying Your FRTS Configuration 357
Understanding Distributed Technologies 359
DCEF 360
DWRED 360
Configuring, Verifying, and Troubleshooting
Link Fragmentation and Interleaving (LFI) 362
Configuring LFI 362
Multilink PPP 362
LFI and Frame Relay 364
Verifying Your LFI Configuration 365
Troubleshooting MLP 366
Configuring, Verifying, and Troubleshooting
RTP Header Compression 367
Configuring RTP Header Compression 368
Verifying Your RTP Header Configuration 368
Troubleshooting RTP Header Compression 369
Summary 370
FAQs 372
Chapter 10 Overview: Border Gateway Protocol (BGP) 375
Introduction 376
The History of BGP 376
Exterior Gateway Protocol (EGP) 376
The Original Implementation 377
The Current RFC 378
Maximizing the Functionality of BGP 380
The BGP Routing Process 380
BGP Finite State Machine Logic 381

Defining the Remote AS 425
Public versus Private Autonomous Systems 426
Enabling BGP Routing 426
Configuring EBGP Neighbors 427
Defining the Remote Version 428
Removing Private AS Numbers 429
Configuring IBGP Neighbors 432
Peering to Loopback Interfaces 432
Configuring Route Reflectors 433
Configuring Confederations 436
When Do I Need Route Reflectors and Confederations? 438
Weight, MED, LOCAL PREF, and Other Advanced Options 439
Route-Map, Match, and Set Commands 441
Weight Attribute 442
Setting the Weight Attribute Using the
Neighbor Statement 442
Setting the Weight Attribute Using Access Lists 443
Setting the Weight Attribute Using Route Maps 444
Multiexit Discriminate (MED) Attribute 444
Setting the MED Attribute Using the
Set Metric Command 445
Setting the MED Attribute with the
Default-Metric Command 446
Local Preference Attribute 446
Setting Local Preference with the Default
Local-Preference Command 447
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xxii Contents
Setting the Local Preference Attribute with
the Set Local-Preference Command 448

110_QoS_ToC 2/14/01 9:07 AM Page xxii
Administering Cisco QoS in IP Networks discusses IP Quality of Service (QoS) and
how it applies to Enterprise and Service Provider environments. It reviews routing
protocols and quality of service mechanisms available today on Cisco network
devices (routers, switches, etc.).This guide provides examples and exercises for a
hands-on experience to give you the background and necessary details to implement
these capabilities in your network today.
The business impact of QoS on major enterprises today ensures the delivery of
the right information necessary to the bottom-line success of the business. QoS
expedites the handling of mission-critical applications, while sharing network
resources with non-critical applications.Today, with Cisco products, QoS has finally
found its time by effectively providing algorithms to ensure delivery that was once
only promised.
Over the past couple of years, the number of methods or protocols for setting
quality of service (QoS) in network equipment has increased dramatically. Advanced
queuing algorithms, traffic shaping, and access-list filtering, have made the process of
choosing a QoS strategy a much more daunting task. All networks can take advantage
of aspects of QoS for optimum efficiency, whether the network is for a small corpo-
ration, an enterprise, or an Internet Service Provider (ISP).
Through Callisma’s skilled team of technology, operations, and project manage-
ment professionals, we enable today’s Enterprises and Service Providers to design and
deploy networks that deliver business value.We help our clients compete effectively
in the new e-business marketplace through strategic business planning, network
design, and implementation services.
—Ralph Troupe, President and CEO
Callisma
Foreword
xxiii
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