Networking Concepts for the Passport 8000 Series Switch

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Part No. 313196-A Rev 00
October 2001
4401 Great America Parkway
Santa Clara, CA 95054
Networking Concepts for the
Passport 8000 Series Switch

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313196-A Rev 00

Copyright © 2001 Nortel Networks
All rights reserved. October 2001.
The information in this document is subject to change without notice. The statements, configurations, technical data, and
recommendations in this document are believed to be accurate and reliable, but are presented without express or implied
warranty. Users must take full responsibility for their applications of any products specified in this document. The
information in this document is proprietary to Nortel Networks Inc.
The software described in this document is furnished under a license agreement and may be used only in accordance
with the terms of that license. The software license agreement is included in this document.
Trademarks
Nortel Networks, the Nortel Networks logo, the Globemark, Unified Networks, Passport, and BayStack are trademarks
of Nortel Networks.
Microsoft, Windows, and Windows NT are trademarks of Microsoft Corporation.
Adobe and Acrobat Reader are trademarks of Adobe Systems Incorporated.
Statement of conditions
In the interest of improving internal design, operational function, and/or reliability, Nortel Networks Inc. reserves the
right to make changes to the products described in this document without notice.
Nortel Networks Inc. does not assume any liability that may occur due to the use or application of the product(s) or
circuit layout(s) described herein.
Federal Communications Commission (FCC) Compliance Notice: Radio Frequency Notice
Note: This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to
Part 15 of the FCC rules. These limits are designed to provide reasonable protection against harmful interference when
the equipment is operated in a commercial environment. This equipment generates, uses, and can radiate radio frequency
energy. If it is not installed and used in accordance with the instruction manual, it may cause harmful interference to
radio communications. Operation of this equipment in a residential area is likely to cause harmful interference, in which
case users will be required to take whatever measures may be necessary to correct the interference at their own expense.
EN 55 022 statement
This is to certify that the Nortel Networks Passport 8000 Series switch is shielded against the generation of radio
interference in accordance with the application of Council Directive 89/336/EEC, Article 4a. Conformity is declared by
the application of EN 55 022 Class A (CISPR 22).
Warning: This is a Class A product. In a domestic environment, this product may cause radio interference, in which
case, the user may be required to take appropriate measures.
Achtung: Dieses ist ein Gerät der Funkstörgrenzwertklasse A. In Wohnbereichen können bei Betrieb dieses Gerätes
Rundfunkstörungen auftreten, in welchen Fällen der Benutzer für entsprechende Gegenmaßnahmen verantwortlich ist.
Attention: Ceci est un produit de Classe A. Dans un environnement domestique, ce produit risque de créer des
interférences radioélectriques, il appartiendra alors à lutilisateur de prendre les mesures spécifiques appropriées.
To maintain compliance with FCC radio frequency emission limits, shielded cables are required to connect equipment to
other Class A certified devices and the use of quadshield, RG-6/U type CATV cable is required for connection to the
CATV system. Any changes or modifications may void the users authorization to operate this equipment.
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Networking Concepts for the Passport 8000 Series Switch

EC Declaration of Conformity
This product conforms (or these products conform) to the provisions of the R&TTE Directive 1999/5/EC.
Japan/Nippon requirements
Voluntary Control Council for Interference (VCCI) statement
Taiwan requirements
Bureau of Standards, Metrology and Inspection (BSMI) Statement
Canada requirements
Canadian Department of Communications Radio Interference Regulations
This digital apparatus (Passport 8000 Series switch) does not exceed the Class A limits for radio-noise emissions from
digital apparatus as set out in the Radio Interference Regulations of the Canadian Department of Communications.
Règlement sur le brouillage radioélectrique du ministère des Communications
Cet appareil numérique (Passport 8000 Series switch) respecte les limites de bruits radioélectriques visant les appareils
numériques de classe A prescrites dans le Règlement sur le brouillage radioélectrique du ministère des Communications
du Canada.
Canada CS-03 rules and regulations
Notice: The Industry Canada label identifies certified equipment. This certification means that the equipment meets
telecommunications network protective, operational and safety requirements as prescribed in the appropriate Terminal
Equipment Technical Requirements document(s). The Department does not guarantee the equipment will operate to the
users satisfaction.
Before installing this equipment, users should ensure that it is permissible to be connected to the facilities of the local
telecommunications company. The equipment must also be installed using an acceptable method of connection. The
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313196-A Rev 00

customer should be aware that compliance with the above conditions may not prevent the degradation of service in some
situations.
Repairs to certified equipment should be coordinated by a representative designated by the supplier. Any repairs or
alterations made by the user to this equipment, or equipment malfunctions, may give the telecommunications company
cause to request the user to disconnect the equipment.
Users should ensure for their own protection that the electrical ground connections of the power utility, telephone lines
and internal metallic water pipe system, if present, are connected together. This precaution may be particularly important
in rural areas.
Caution: Users should not attempt to make such connections themselves, but should contact the appropriate electric
inspection authority, or electrician, as appropriate.
Notice: For equipment using loopstart lines, please note that the Ringer Equivalence Number (REN) assigned to each
terminal device provides an indication of the maximum number of terminals allowed to be connected to a telephone
interface. The termination on an interface may consist of any combination of devices subject only to the requirement that
the sum of the Ringer Equivalence Numbers of all the devices does not exceed 5. The REN is located on the FCC Rules
Part 68 label located on the bracket of the module, or on the back of the unit.
Canada CS-03 -- règles et règlements
Avis: L'étiquette d'Industrie Canada identifie le matériel homologué. Cette étiquette certifie que le matériel est conforme
aux normes de protection, d'exploitation et de sécurité des réseaux de télécommunications, comme le prescrivent les
documents concernant les exigences techniques relatives au matériel terminal. Le Ministère n'assure toutefois pas que le
matériel fonctionnera à la satisfaction de l'utilisateur.
Avant d'installer ce matériel, l'utilisateur doit s'assurer qu'il est permis de le raccorder aux installations de l'entreprise
locale de télécommunication. Le matériel doit également être installé en suivant une méthode acceptée de raccordement.
L'abonné ne doit pas oublier qu'il est possible que la conformité aux conditions énoncées ci-dessus n'empêche pas la
dégradation du service dans certaines situations.
Les réparations de matériel homologué doivent être coordonnées par un représentant désigné par le fournisseur.
L'entreprise de télécommunications peut demander à l'utilisateur de débrancher un appareil à la suite de réparations ou
de modifications effectuées par l'utilisateur ou à cause de mauvais fonctionnement.
Pour sa propre protection, l'utilisateur doit s'assurer que tous les fils de mise à la terre de la source d'énergie électrique,
des lignes téléphoniques et des canalisations d'eau métalliques, s'il y en a, sont raccordés ensemble. Cette précaution est
particulièrement importante dans les régions rurales.
Avertissement: L'utilisateur ne doit pas tenter de faire ces raccordements lui-même; il doit avoir recours à un service
d'inspection des installations électriques, ou à un électricien, selon le cas.
Avis: Veuillez prendre note que pour tout appareillage supportant des lignes de type loopstart, l'indice d'équivalence
de la sonnerie (IES) assigné à chaque dispositif terminal indique le nombre maximal de terminaux qui peuvent être
raccordés à une interface. La terminaison d'une interface téléphonique peut consister en une combinaison de quelques
dispositifs, à la seule condition que la somme d'indices d'équivalence de la sonnerie de tous les dispositifs n'excède pas
5. Le REN figure sur létiquette FCC Rules Part 68 située sur le support du module ou à larrière de lunité.
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Networking Concepts for the Passport 8000 Series Switch

Nortel Networks Inc. software license agreement
This Software License Agreement (License Agreement) is between you, the end-user (Customer) and Nortel
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313196-A Rev 00

4.General
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and Nortel Networks.
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Software is acquired in the United States, then this License Agreement is governed by the laws of the state of New York.
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Networking Concepts for the Passport 8000 Series Switch

Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Before you begin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Text conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Related publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
How to get help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Chapter 1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Passport 8000 Series hardware and software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
New software features in the current release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Networking concepts in the Passport 8000 Series switch . . . . . . . . . . . . . . . . . . . . . .34
Chapter 2
Network management and diagnostics. . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Port mirroring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 9
Syslog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Network Time Protocol (NTP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
NTP terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
NTP system implementation model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
How NTP distributes time within a subnet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Synchronizing with the best available time server . . . . . . . . . . . . . . . . . . . . . . . . .44
NTP modes of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
NTP authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
8 Contents
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Chapter 3
Network layers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Network schemes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47
Network processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
OSI layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
Internet Protocol layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
Types of service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
IEEE 802 LANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54
Chapter 4
VLANs, Spanning Tree, and MultiLink Trunking. . . . . . . . . . . . . . . . . . . . . 55
Overview of VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
Port-based VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
Policy-based VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
Protocol-based VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
Source MAC-based VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60
Source IP subnet-based VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61
VLAN tagging and port types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62
802.1Q tagged ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63
Treatment of tagged and untagged frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64
IP and IPX routing and VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
IP routing and VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
IPX routing and VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
Passport 8000 Series switch VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66
Special VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66
Default VLAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66
Unassigned VLAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66
Brouter port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
VLAN rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
Summary of VLAN features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68
Spanning Tree Protocol (STP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
Spanning tree groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
Spanning Tree Protocol controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70
Spanning Tree FastStart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
MultiLink Trunking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
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MultiLink Trunking rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
MultiLink Trunking examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
Switch-to-switch MLT configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
Switch-to-server MLT configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74
Client/server MLT configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74
Split MultiLink Trunking (SMLT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76
Advantages OF SMLT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
Single point of failure elimination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
STP convergence issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
SMLT terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79
How does SMLT work? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80
Inter-switch trunk (IST) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .81
Switch connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82
SMLT and VRRP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83
VRRP backup master . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84
Chapter 5
IP routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
IP addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85
Subnet addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86
Supernet addressing and CIDR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .88
Types of IP routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90
Virtual routing between VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90
Brouter ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91
Static routes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91
Black hole static routes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92
IP enhancements and policies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93
Equal Cost MultiPath (ECMP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93
Alternate route . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93
Route filtering/IP policies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95
Accept policies/in filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96
Redistribution filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96
Announce policies/out filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96
Route filtering stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97
Prefix list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
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Route policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
Configuration sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
PPP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100
Establishing the PPP link . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100
Negotiating network layer protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
IP over PPP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102
IPX over PPP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102
IP connectivity protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103
Address Resolution Protocol (ARP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104
Proxy ARP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104
Flushing router tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .105
BootP/DHCP relay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .105
Differences between DHCP and BootP . . . . . . . . . . . . . . . . . . . . . . . . . . . .106
Summary of DHCP relay operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106
Forwarding DHCP packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107
Multiple BootP/DHCP servers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108
UDP broadcast forwarding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109
Reverse Address Resolution Protocol (RARP) . . . . . . . . . . . . . . . . . . . . . . . . . .110
Virtual Router Redundancy Protocol (VRRP) . . . . . . . . . . . . . . . . . . . . . . . . . . .110
Chapter 6
RIP and OSPF. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Routing Information Protocol (RIP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113
Open Shortest Path First (OSPF) Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
OSPF routing algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116
Autonomous system and areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .117
Backbone area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .117
Stub area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .118
Not so stubby area (NSSA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .118
Neighbors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .118
Neighbors on NBMA networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119
Neighbor adjacencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119
NBMA adjacencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .120
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OSPF routers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .120
Router types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121
OSPF interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121
Broadcast interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .122
Non-broadcast multiaccess interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .122
Passive interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .126
OSPF and IP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127
OSPF packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127
Link state advertisements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .128
AS external routes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129
OSPF virtual links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129
Specifying ASBRs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .130
Metric Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .130
Chapter 7
IP Multicast. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
Overview of IP Multicast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133
Multicast host groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134
Multicast addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135
Multicast protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136
Internet Group Management Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136
IGMP concepts and terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137
IGMP queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137
IGMP host reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137
Host leave messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .138
Fast leave feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .138
Passport 8000 Series IGMP implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . .139
IGMP snoop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139
IGMP proxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .140
Multicast Router Discovery Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .140
Distance Vector Multicast Routing Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .141
Reverse path forwarding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .142
Pruning and grafting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .142
DVMRP concepts and terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .142
Neighbor connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143
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Source route advertisements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143
How DVMRP chooses a route . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .144
Routing table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .144
Shortest-path trees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145
Static source groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145
Passport 8000 Series implementation of DVMRP . . . . . . . . . . . . . . . . . . . . . . . .146
Protocol Independent Multicast - Sparse Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . .147
PIM-SM terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .147
Hosts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .148
PIM-SM domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .148
Designated router (DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .148
Rendezvous-Point (RP) router . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149
Bootstrap router . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149
Join/prune messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .150
Register and register-stop messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .150
Shared trees and shortest-path trees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .150
Shared trees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .151
Shortest-path trees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .151
Receiver joining group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .153
Receiver leaving group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .153
Source sending packets to group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .153
Required elements for PIM-SM operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .154
PIM-SM simplified example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .155
Pragmatic General Multicast (PGM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .156
PGM terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .156
Transport session identifiers (TSIs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157
Source path messages (SPMs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157
Negative acknowledgements (NAKs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157
NAK confirmations (NCFs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157
Designated local repairers (DLRs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158
PGM network element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158
Contents 13
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Chapter 8
IPX routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
IPX protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 9
IPX packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .162
IPX traffic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .164
Passport 8000 Series IPX network-layer support . . . . . . . . . . . . . . . . . . . . . . . . . . .165
Routing Information Protocol (RIP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .165
Service Advertising Protocol (SAP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167
Broadcast techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .168
Best route algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .169
Split horizon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .169
NetBIOS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 0
Static routes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 2
Static SAP services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .172
IPX default static routes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .172
Chapter 9
Quality of Service, DiffServ, and IP filtering . . . . . . . . . . . . . . . . . . . . . . . 173
Quality of Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .173
QoS and LAN traffic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .174
DiffServ network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175
Packet classification and marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .176
Per-hop behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .176
Assured Forwarding PHB group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177
Expedited Forwarding PHB group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177
Policing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177
Passport 8000 Series implementation of DiffServ . . . . . . . . . . . . . . . . . . . . . . . . . . .177
DiffServ access port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .178
Tagged traffic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .180
Untagged traffic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182
DiffServ core port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183
Tagged traffic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184
Untagged traffic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184
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Classification and policing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184
Rate metering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185
Priority queuing and servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187
IP filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188
Enabling ARP traffic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .189
Source and destination filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191
Global filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191
Filter configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192
Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193
Chapter 10
ATM networking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
ATM elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195
User network interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196
Quality of Service (QoS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196
LAN-to-LAN connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196
ATM characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197
Cell size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197
Header format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197
Adaptation layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198
Category of service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198
AAL support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .199
ATM speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .199
Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .199
LLC encapsulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200
Null encapsulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200
Passport 8672ATM Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200
Chapter 11
Optical networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
SONET/SDH networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203
SONET/SDH speeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .204
SONET/SDH layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .204
SONET/SDH ring architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205
Contents 15
Networking Concepts for the Passport 8000 Series Switch

Packet-over-SONET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205
PPP over SONET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .206
Physical layer requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .206
Interface format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .206
Transmission rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .206
Control signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .206
Frame format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207
Flag Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207
Address field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207
Control field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208
Frame Check Sequence (FCS) field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208
Configuration details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208
PPP Bridging Control Protocol (BCP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209
Passport 8683POSE Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209
Wavelength Division Multiplexing (WDM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209
Passport 8600 Switch CWDM optical routing . . . . . . . . . . . . . . . . . . . . . . . . . . .210
Point-to-Point architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .212
Ring architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .212
Transmission distances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .213
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
16 Contents
313196-A Rev 00
17
Networking Concepts for the Passport 8000 Series Switch

Figures
Figure 1 NTP time servers forming a synchronization subnet . . . . . . . . . . . . . . . .43
Figure 2 NTP time servers operating in unicast client mode . . . . . . . . . . . . . . . . .45
Figure 3 Seven layers of the OSI Reference Model . . . . . . . . . . . . . . . . . . . . . . . .49
Figure 4 Four layers of the IP stack model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
Figure 5 Port-based VLAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
Figure 6 Dynamic protocol-based VLAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58
Figure 7 Incorrect use of an IP subnet-based VLAN . . . . . . . . . . . . . . . . . . . . . . .62
Figure 8 VLAN tag insertion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63
Figure 9 Multiple spanning tree groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70
Figure 10 Switch-to-switch MLT configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
Figure 11 Switch-to-server MLT configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74
Figure 12 Client/Server MLT configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75
Figure 13 Resilient networks with Spanning Tree Protocol . . . . . . . . . . . . . . . . . . .78
Figure 14 Resilient networks with SMLT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79
Figure 15 Passport 8600 Switches as SMLT aggregation switches . . . . . . . . . . . . .81
Figure 16 Network and host boundaries in IP address classes . . . . . . . . . . . . . . . .86
Figure 17 Class C address supernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89
Figure 18 IP routing between VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90
Figure 19 Route filtering for unicast routing protocols . . . . . . . . . . . . . . . . . . . . . . .95
Figure 20 Route filtering stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97
Figure 21 Route filtering logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98
Figure 22 Proxy ARP operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .105
Figure 23 DHCP operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107
Figure 24 Forwarding DHCP packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107
Figure 25 Configuring multiple BootP/DHCP servers . . . . . . . . . . . . . . . . . . . . . . .108
Figure 26 Virtual Router Redundancy Protocol configuration . . . . . . . . . . . . . . . . . 111
Figure 27 Hop count or metric in RIP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114
Figure 28 NBMA subnet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123
Figure 29 NBMA subnet configuration example . . . . . . . . . . . . . . . . . . . . . . . . . . .125
18 Figures
313196-A Rev 00
Figure 30 Virtual link between ABRs through a transit area . . . . . . . . . . . . . . . . . .130
Figure 31 Multicast distribution tree and broadcasting . . . . . . . . . . . . . . . . . . . . . .133
Figure 32 Pruning routers from a distribution tree . . . . . . . . . . . . . . . . . . . . . . . . .134
Figure 33 Shared tree and shortest-path tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . .152
Figure 34 PIM-SM simplified example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .155
Figure 35 IPX internetwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161
Figure 36 IPX internetwork packet exchange header . . . . . . . . . . . . . . . . . . . . . . .163
Figure 37 IPX packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .163
Figure 38 IPX addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .164
Figure 39 IPX-RIP packet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166
Figure 40 IPX-SAP packet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .168
Figure 41 Best route algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .169
Figure 42 Split horizon enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .170
Figure 43 NetBIOS support in a NetWare environment . . . . . . . . . . . . . . . . . . . . .171
Figure 44 DiffServ network model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .178
Figure 45 DiffServ access port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .179
Figure 46 PPP HDLC frame structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207
Figure 47 Typical CWDM point-to-point architecture . . . . . . . . . . . . . . . . . . . . . . .212
Figure 48 Typical CWDM ring architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .213
19
Networking Concepts for the Passport 8000 Series Switch

Tables
Table 1 Chassis options for a Passport 8000 Series switch . . . . . . . . . . . . . . . . .30
Table 2 Module options for a Passport 8600 Switch . . . . . . . . . . . . . . . . . . . . . . .31
Table 3 Module options for a Passport 8100 Switch . . . . . . . . . . . . . . . . . . . . . . .32
Table 4 Convertors and adaptors for a Passport 8000 Series switch . . . . . . . . . .32
Table 5 New and enhanced features in the Passport 8000 Series
software, release 3.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Table 6 Reserved PIDs for user-defined protocol-based VLANs . . . . . . . . . . . . .59
Table 7 VLANs, STGs, and MLTs in the Passport 8000 Series switch . . . . . . . . .68
Table 8 IP addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85
Table 9 Subnet masks for Class B and Class C IP addresses . . . . . . . . . . . . . . .87
Table 10 Router types in an OSPF network . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121
Table 11 Parts of a routing table entry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .144
Table 12 DiffServ terms and concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175
Table 13 Ingress DSCP and IEEE 802.1p to QoS level mapping . . . . . . . . . . . . .180
Table 14 Egress QoS level to DSCP and IEEE 802.1p mapping . . . . . . . . . . . . .181
Table 15 Access port actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183
Table 16 Core port actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184
Table 17 10 Mb/s Ethernet line rate metering . . . . . . . . . . . . . . . . . . . . . . . . . . . .185
Table 18 100 Mb/s Ethernet line rate metering . . . . . . . . . . . . . . . . . . . . . . . . . . .186
Table 19 Gigabit Ethernet line rate metering . . . . . . . . . . . . . . . . . . . . . . . . . . . . .186
Table 20 Traffic service classes mapping to QoS levels . . . . . . . . . . . . . . . . . . . .187
Table 21 Port actions for filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193
Table 22 SONET/SDH speeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .204
Table 23 Optical routing system components . . . . . . . . . . . . . . . . . . . . . . . . . . . .211
20 Tables
313196-A Rev 00
21
Networking Concepts for the Passport 8000 Series Switch

Preface
Nortel Networks* Passport 8000 Series* 8000 Series switch is flexible and
multifunctional, supporting a diverse range of network architectures and
protocols. This guide to networking concepts for the Passport 8000 Series switch
provides a general description of the design principles underlying core and
optional operational features. A companion book to this guide, Network Design
Guidelines for the Passport 8000 Series Switch, outlines a range of network
design scenarios to assist you in optimizing network performance.
Before you begin
This guide is intended for network designers and administrators with the
following background:
 Basic knowledge of networks, Ethernet bridging, and IP and IPX routing
 Familiarity with networking concepts and terminology
 Basic knowledge of network topologies
 Experience with windowing systems or graphical user interfaces (GUIs)
22 Preface
313196-A Rev 00

Text conventions
This guide uses the following text conventions:
angle brackets (< >) Indicate that you choose the text to enter based on the
description inside the brackets. Do not type the
brackets when entering the command.
Example: If the command syntax is
ping <ip_address>
, you enter
ping 192.32.10.12
bold Courier text
Indicates command names and options and text that
you need to enter.
Example: Use the
dinfo
command.
Example: Enter
show ip

{alerts|routes}
.
braces ({}) Indicate required elements in syntax descriptions where
there is more than one option. You must choose only
one of the options. Do not type the braces when
entering the command.
Example: If the command syntax is
show ip {alerts|routes}
, you must enter either
show ip alerts
or
show ip routes
, but not both.
brackets ([ ]) Indicate optional elements in syntax descriptions. Do
not type the brackets when entering the command.
Example: If the command syntax is
show ip interfaces [-alerts]
, you can enter
either
show ip interfaces

or

show ip interfaces -alerts
.
ellipsis points (. . . ) Indicate that you repeat the last element of the
command as needed.
Example: If the command syntax is
ethernet/2/1 [<parameter> <value>]...

,
you enter
ethernet/2/1

and as many
parameter-value pairs as needed.
Preface 23
Networking Concepts for the Passport 8000 Series Switch

Related publications
For more information about using a Passport 8000 Series switch, the resident CLI,
or Device Manager, refer to the following publications:
 Release Notes for the Passport 8000 Series Switch Release 3.2 (part number
313946-A Rev 00)
italic text Indicates new terms, book titles, and variables in
command syntax descriptions. Where a variable is two
or more words, the words are connected by an
underscore.
Example: If the command syntax is
show at
<valid_route>, valid_route

is one
variable and you substitute one value for it.
plain Courier
text
Indicates command syntax and system output, for
example, prompts and system messages.
Example:
Set Trap Monitor Filters
separator ( > ) Shows menu paths.
Example: Protocols > IP identifies the IP command on
the Protocols menu.
vertical line (
|
) Separates choices for command keywords and
arguments. Enter only one of the choices. Do not type
the vertical line when entering the command.
Example: If the command syntax is
show ip {alerts|routes}
, you enter either
show ip alerts
or
show ip routes
, but not
both.
24 Preface
313196-A Rev 00

Provides a list of new features and late-breaking information about the
hardware and software that is not included in the Passport 8000 Series switch
documentation.
 Installing and Maintaining the Passport 8003 Chassis and Components
(part number 313074-B Rev 00)
Provides instructions for installing the Passport 8000 Series 8003 Chassis in
an equipment rack and for installing and replacing fan trays, power supplies,
modules, gigabit interface converters, and media dependent adapters. This
guide describes some of the routine tasks of operating the Passport 8000
Series 8003 Chassis and includes technical specifications for the chassis and
the modules.
 Installing and Maintaining the Passport 8006 Chassis and Components
(part number 312748-B Rev 00)
Provides instructions for installing the Passport 8000 Series 8006 Chassis in
an equipment rack and for installing and replacing fan trays, power supplies,
modules, gigabit interface converters, and media dependent adapters. This
guide describes some of the routine tasks of operating the Passport 8000
Series 8006 Chassis and includes technical specifications for the chassis and
the modules.
 Installing and Maintaining the Passport 8010 Chassis and Components
(part number 312747-B Rev 00)
Provides instructions for installing the Passport 8000 Series 8010 Chassis in
an equipment rack and for installing and replacing fan trays, power supplies,
modules, gigabit interface converters, and media dependent adapters. This
guide describes some of the routine tasks of operating the Passport 8000
Series 8010 Chassis and includes technical specifications for the chassis and
the modules.
 Installing and Maintaining the Passport 8010co Chassis and Components
(part number 312746-B Rev 00)
Provides instructions for installing the Passport 8000 Series 8010co Chassis in
an equipment rack and for installing and replacing fan trays, power supplies,
modules, gigabit interface converters, and media dependent adapters. This
guide describes some of the routine tasks of operating the Passport 8000
Series 8010co Chassis and includes technical specifications for the chassis
and the modules.
Preface 25
Networking Concepts for the Passport 8000 Series Switch

 Installing the Breaker Interface Panel for the Passport 8010co Chassis
(part number 312755-B Rev 00)
Describes how to install the breaker interface panel in an equipment rack,
connect cables, and interpret LEDs. It includes technical specifications for the
breaker interface panel.
 Networking Concepts for the Passport 8000 Series Switch (part number
313196-A Rev 00)
Provides general information and a description of how a Passport 8000 Series
switch handles various networking features, such as VLANs, MultiLink
Trunking, OSPF, RIP, and IPX.
 Network Design Guidelines for the Passport 8000 Series Switch (part number
313197-A Rev 00)
Provides guidelines for using the switching and routing features of the
Passport 8000 Series hardware and software in your network design. This
companion guide to Networking Concepts for the Passport 8000 Series Switch
incorporates feedback from beta testing of the switch and focuses on
optimizing network performance.
 Getting Started with the Passport 8000 Series Switch Management Software
(part number 313189-B Rev 00)
Provides instructions for installing the Passport 8000 Series switch
management software and describes initial setup procedures.
 Managing the Passport 8000 Series Switch Using the Command Line
Interface Release 3.2 (part number 313194-B Rev 00)
Describes the command line interface (CLI) structure and the commands used
to perform basic switch management operations, such as modifying the switch
boot sequence, working with switch files, and setting up security features.
 Configuring Switching and Routing Operations for the Passport 8000 Series
Switch Using the Command Line Interface Release 3.2 (part number
313191-B Rev 00)
Describes the CLI commands and parameters for configuring layer 2
(switching) and layer 3 (routing) operations.
26 Preface
313196-A Rev 00

 Managing the Passport 8000 Series Switch Using Device Manager Release
5.x.x (part number 313195-B Rev 00)
Describes the structure of Device Manager and how to use it to perform basic
switch management operations, such as working with switch files and setting
up security features.
 Configuring Switching and Routing Operations for the Passport 8000 Series
Switch Using Device Manager Release 5.x.x (part number 313193-A Rev 00)
Describes how to use Device Manager to configure and manage layer 2
(switching) and layer 3 (routing) functions.
You can print selected technical manuals and release notes free, directly from the
Internet. Go to the www.nortelnetworks.com/documentation URL. Find the
product for which you need documentation. Then locate the specific category and
model or version for your hardware or software product. Use Adobe* Acrobat
Reader* to open the manuals and release notes, search for the sections you need,
and print them on most standard printers. Go to Adobe Systems at the
www.adobe.com URL to download a free copy of the Adobe Acrobat Reader.
You can purchase selected documentation sets, CDs, and technical publications
through the Internet at the www1.fatbrain.com/documentation/nortel/ URL.
How to get help
If you purchased a service contract for your Nortel Networks product from a
distributor or authorized reseller, contact the technical support staff for that
distributor or reseller for assistance.
If you purchased a Nortel Networks service program, contact one of the following
Nortel Networks Technical Solutions Centers:
Technical Solutions Center Telephone
Europe, Middle East, and Africa (33) (4) 92-966-968
North America (800) 4NORTEL or (800) 466-7835
Asia Pacific (61) (2) 9927-8800
China (800) 810-5000
Preface 27
Networking Concepts for the Passport 8000 Series Switch

Additional information about the Nortel Networks Technical Solutions Centers is
available from the www.nortelnetworks.com/help/contact/global URL.
An Express Routing Code (ERC) is available for many Nortel Networks products
and services. When you use an ERC, your call is routed to a technical support
person who specializes in supporting that product or service. To locate an ERC for
your product or service, go to the http://www130.nortelnetworks.com/cgi-bin/
eserv/common/essContactUs.jsp URL.
28 Preface
313196-A Rev 00

29
Networking Concepts for the Passport 8000 Series Switch

Chapter 1
Introduction
The Passport 8000 Series switch is a modular multipurpose device that provides
fast and reliable communication for LANs, MANs, and WANs. Modules
supporting many different networking functions can be combined in a single
device. A combination of Passport 8000 Series modules enables you to offer the
following capabilities in a single device:
 Bridging and switching
 Virtual LANs (VLANs)
 IP routing
 IPX routing
 Quality of Service
 Asynchronous transfer mode (ATM) interface
 Synchronous optical networking (SONET) interface
 Wavelength Division Multiplexing (WDM)
This guide summarizes the general networking concepts used in the Passport 8000
Series switches that include routing switch modules and edge switch modules.
For detailed information about implementing these functions using the Device
Manager graphical user interface (GUI), refer to these books:
 Configuring Switching Operations for the Passport 8000 Series Switch Using
Device Manager Release 5.1.x
 Configuring Switching and Routing Operations for the Passport 8000 Series
Switch Using Device Manager Release 5.x.x.
For implementation using the command line interface (CLI), refer to these books:
 Managing the Passport 8000 Series Switch Using the Command Line
Interface Release 3.2
30 Chapter 1 Introduction
313196-A Rev 00

 Configuring Switching Operations for the Passport 8000 Series Switch Using
the Command Line Interface Release 3.1.2
 Configuring Switching and Routing Operations for the Passport 8000 Series
Switch Using the Command Line Interface Release 3.2.
Passport 8000 Series hardware and software
A Passport 8000 Series switch is composed of a Passport 8000 Series chassis that
has either routing switch or edge switch modules installed in it. Passport 8600
modules perform routing and switching functions. Passport 8100 modules
perform edge switch functions.
Routing and switching functions on the Passport 8600 modules are deployed
flexibly to deliver high-performance switching and traditional routing services as
required. The Passport 8100 modules offer high-performance, high-density
switching. These modules installed in a Passport 8000 Series chassis create an
edge switch entity within the chassis. Table 1 lists the chassis options that are
currently available for the Passport 8000 Series switch.
Table 1 Chassis options for a Passport 8000 Series switch
Chassis Description
8003 Chassis 3-slot chassis
8006 Chassis 6-slot chassis
8010 Chassis 10-slot chassis
8010co Chassis 10-slot carrier-grade chassis
Chapter 1 Introduction 31
Networking Concepts for the Passport 8000 Series Switch

Table 2 lists the nodule options currently available for the Passport 8600 Switch.
Table 2 Module options for a Passport 8600 Switch
Passport 8600 module Description
8690SF Switch fabric/CPU module
8648TX 48-port 10BASE-T/100BASE-TX
8648TXE 48-port 10BASE-T/100BASE-TX  E-module
8624FX 24-port 100BASE-FX
8624FXE 24-port 100BASE-FX  E-module
8608SX 24-port 1000BASE-SX
8608SXE 24-port 1000BASE-SX  E-module
8616SX 16-port 1000BASE-SX
8616SXE 16-port 1000BASE-SX  E-module
8608GT 8-port 1000BASE-T
8608GTE 8-port 1000BASE-T  E-module
8608GB
1
1 Gigabit Ethernet ports connect to Gigabit Interface Convertors (GBICs). A list of GBICS is
provided in Table 4.
8-port Gigabit Ethernet
8608GBE 8-port Gigabit Ethernet  E-module
8632TXE 32-port 10BASE-T/100BASE-TX + 2 Gigabit Ethernet ports
8672ATM
2
2 ATM modules connect to an ATM Media Dependent Adaptor (MDA). A list of ATM MDAs is
provided in Table 4.
ATM module
8672ATME ATM module  E-module
8683POS
3
3 POS modules connect to a POS MDA. A list of POS MDAs is provided in Table 4.
Packet over SONET module
8683POSE Packet over SONET module  E-module
32 Chapter 1 Introduction
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Table 3 lists the modules that are currently available for the Passport 8100 Switch.
Table 3 Module options for a Passport 8100 Switch
Table 4 lists the Gigabit Ethernet interface convertors (GBICs) and the media
dependent adaptors (MDAs) currently available for the Passport 8000 Series
switch.
Table 4 Convertors and adaptors for a Passport 8000 Series switch
Module Description
8190 SM Switch management module
8132TX 32-port 10BASE-T/100BASE-TX
8116FX 16-port 100BASE-FX
8148TX 48-port 100BASE-TX
8108GBIC
1
1 Gigabit Ethernet ports connect to GBICs. A list of available GBICs is provided in Table 4.
8-port Gigabit Ethernet module
Convertor/adaptor Description Related modules
GBIC 1000BASE-SX 8632TXE, 8608GB,
8608GBE, 8108GBIC
1000BASE-LX
1000BASE-XD
1000BASE-ZX
1000BASEWDM 1470nm Wavelength
1000BASEWDM 1490nm Wavelength
1000BASEWDM 1510nm Wavelength
1000BASEWDM 1530nm Wavelength
1000BASEWDM 1550nm Wavelength
1000BASEWDM 1570nm Wavelength
1000BASEWDM 1590nm Wavelength
1000BASEWDM 1610nm Wavelength
Chapter 1 Introduction 33
Networking Concepts for the Passport 8000 Series Switch

Protocols and concepts described in this book require the following software
releases:
 Release 3.2 and higher for the Passport 8600 modules
 Release 2.0 and higher for the Passport 8100 modules
New software features in the current release
A range of new software features are provided in the Passport 8000 Series switch,
release 3.2. Table 5 lists these features with references to where these features are
described in this book.
ATM MDA 4-port OC-3 MM 8672ATM, 8672ATME
4-port OC-3 SM
4-port OC-12 MM
4-port OC-12 SM
POS MDA 4-port OC-3 MM 8683POS, 8683POSE
4-port OC-3 SM
1-port OC-12 MM
1-port OC-12 SM
Table 5 New and enhanced features in the Passport 8000 Series software, release 3.2
Feature Chapter Page
Layer 2 CPU redundancy Chapter 2, Network
management and diagnostics
page 40
Port mirroring enhancements page 39
Network Time Protocol page 41
Split Multi-Link Trunking Chapter 4, VLANs, Spanning
Tree, and MultiLink Trunking
page 76
IP enhancements and policies Chapter 5, IP routing page 93
Equal Cost MultiPath (ECMP) page 93
OSPF interfaces Chapter 6, RIP and OSPF page 121
Convertor/adaptor Description Related modules
34 Chapter 1 Introduction
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Networking concepts in the Passport 8000 Series switch
Devising a network design that optimizes the features in a Passport 8000 Series
switch requires an understanding of a range of networking concepts. This guide
discusses networking concepts with a special emphasis on how these concepts are
implemented in a Passport 8000 Series switch. This guide assumes that you are
familiar with the basics of bridging/switching, routing, IP addressing, and
Spanning Tree Protocol.
The following information is included in this guide:
 Chapter 2, Network management and diagnostics, on page 37, describes the
different network management tools available for the Passport 8000 Series
switch.
 Chapter 3, Network layers, on page 47, describes OSI and IP layers and
IEEE LAN specifications.
 Chapter 4, VLANs, Spanning Tree, and MultiLink Trunking, on page 55,
describes virtual LANs (VLANs) and related features such as Spanning Tree
Protocol and MultiLink Trunking.
 Chapter 5, IP routing, on page 85, describes IP routing concepts and
protocols.
 Chapter 6, RIP and OSPF, on page 113, describes the IP multicasting
support in Passport 8600 module  IGMP and DVMRP.
 Chapter 7, IP Multicast, on page 133, describes the software support in the
Passport 8600 modules for IPX routing.
 Chapter 8, IPX routing, on page 159, describes how Passport 8600 modules
implement IP filtering for traffic policing and management.
Protocol Independent Multicast -Sparse Mode (PIM-SM) Chapter 7, IP Multicast page 147
Pragmatic General Multicast (PGM) page 156
Static source groups page 145
Coarse Wavelength Division Multiplexing (CWDM) Chapter 11, Optical networks page 210
Table 5 New and enhanced features in the Passport 8000 Series software, release 3.2
Feature Chapter Page
Chapter 1 Introduction 35
Networking Concepts for the Passport 8000 Series Switch

 Chapter 9, Quality of Service, DiffServ, and IP filtering, on page 173,
describes how the Passport 8600 modules support Quality of Service using
the DiffServ architecture.
 Chapter 10, ATM networking, on page 195, describes the networking
concepts implemented in the Passport 8672ATME Module.
 Chapter 11, Optical networks, on page 203, describes SONET/SDH optical
networking standards, packet-over-SONET and the Passport 8683POSE
Module, and Coarse Wavelength Division Multiplexing implemented with
CWDM GBICs.
36 Chapter 1 Introduction
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37
Networking Concepts for the Passport 8000 Series Switch

Chapter 2
Network management and diagnostics
A choice of software applications is available to manage your Passport 8000
Series switch. The Device Manager software application utilizes the Simple
Network Management Protocol (SNMP) to manage your switch through a
graphical user interface (GUI). Alternatively you can manage your Passport 8000
Series switch through the command line interface (CLI). Additionally, you can
view configurations on the switch through a Web interface that can be accessed
through any standard Web browser. For more information, refer to the following
publications:
 For information about using Device Manager, refer to Configuring Switching
Operations for the Passport 8000 Series Switch Using Device Manager
Release 5.1.x and Configuring Switching and Routing Operations for the
Passport 8000 Series Switch Using Device Manager Release 5.x.x.
 For information about using the command line interface (CLI), refer to
Managing the Passport 8000 Series Switch Using the Command Line
Interface Release 3.2, Configuring Switching Operations for the Passport
8000 Series Switch Using the Command Line Interface Release 3.1.2, and
Configuring Switching and Routing Operations for the Passport 8000 Series
Switch Using the Command Line Interface Release 3.2.
 For information about monitoring your Passport 8000 Series switch through a
Web browser, refer to Getting Started with the Passport 8000 Series Switch
Management Software.
By using these management tools, you can configure switching or routing
configurations and enable other features such as RMON alarms and port mirroring
to analyze traffic on a per-port basis.
38 Chapter 2 Network management and diagnostics
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RMON
Remote monitoring (RMON) is a management information base (MIB) or a group
of management objects that you use to get or set values using Simple
Network Management Protocol (SNMP). Using the CLI or Device Manager, you
enable RMON globally for devices on the switch. When RMON is enabled
globally, you then enable monitoring for individual devices on a port-by-port
basis.
RMON has four major functions:
 Setting alarms for user-defined events
 Gathering real-time and historical Ethernet statistics
 Logging events
 Sending traps for events
Within Device Manager, you can set RMON alarms that relate to specific events
or variables simply by selecting these variables from a drop-down menu. You
specify events associated with alarms to be set to either trap or log-and-trap. In
turn, these alarms, when tripped, are trapped or logged.
All RMON information is viewable within both Device Manager and the CLI.
Alternatively you can use any management application that supports SNMP traps
(such as Optivity NMS
*
and HP OpenView*) to view RMON trap information.
Chapter 2 Network management and diagnostics 39
Networking Concepts for the Passport 8000 Series Switch

Port mirroring
Passport 8000 Series switches have a port mirroring feature that helps you to
monitor and analyze network traffic. The port mirroring feature supports both
ingress (incoming traffic) and egress (outgoing traffic) port mirroring. When this
feature is enabled, the mirrored (source) ports ingress or egress packets are
forwarded normally and a copy of the packets is sent out the mirrored port to the
mirroring (destination) port. Although you can configure Passport 8000 Series
switches to monitor both ingress and egress traffic, some restrictions apply:
 Passport 8100 switches
 Ingress port mirroring is always supported
 Egress port mirroring is supported only in half-duplex mode of operation
 Passport 8600 switches
 Ingress port mirroring is always supported
 Egress port mirroring is currently supported only on Passport 8600
E-modules
You can configure up to 100 entries in the port mirroring table for mirroring, and
you can have up to 25 entries active at any given time.
Egress port mirroring can be enabled separately, allowing you to monitor packets
as they leave specified ports. In addition, you can monitor traffic for MAC
addresses, where traffic with a given MAC source address (SA) or MAC
destination address (DA) is copied to the specified mirroring port.
To avoid seeing unintended traffic, you should remove mirroring (destination)
ports from all virtual local area networks (VLANs) and spanning tree groups
(STGs).
You can observe and analyze packet traffic at the mirroring port using a network
analyzer  a copy of the packet can be captured and analyzed. Unlike other
methods that are used to analyze packet traffic, the packet traffic is uninterrupted
and packets flow normally through the mirrored port.
For more information about the port mirroring feature, see:
 Configuring Switching and Routing Operations for the Passport 8000 Series
Switch Using the Command Line Interface Release 3.2.
40 Chapter 2 Network management and diagnostics
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 Configuring Switching and Routing Operations for the Passport 8000 Series
Switch Using Device Manager Release 5.x.x.
Syslog
On any UNIX*-based management platform, you can use the syslog messaging
feature of the Passport 8000 Series 8000 Series switch to manage event messages.
The Passport 8000 Series syslog software communicates with a server software
component named syslogd on your management workstation. The UNIX daemon
syslogd is a software component that receives and locally logs, displays, prints,
and/or forwards messages that originate from sources internal and external to the
workstation. For example, syslogd on a UNIX workstation concurrently handles
messages received from applications running on the workstation, as well as
messages received from a Passport 8000 Series switch running in a network
accessible to the workstation.
For further information about syslog functionality, refer to Configuring Switching
Operations for the Passport 8000 Series Switch Using the Command Line
Interface Release 3.1.2 and Configuring Switching Operations for the Passport
8000 Series Switch Using Device Manager Release 5.1.x.
Redundancy
As system resources become more widely distributed the reliability of network
nodes is even more important since it affects connectivity in the entire network.
While reliability ensures that the software and hardware components of a node are
robust, they are still prone to failures. Protecting the node from failure of any of its
components makes the node highly available.
Many high availability features are built in at all levels of the Passport 8000 Series
switch, including the following:
 Port-level and slot-level redundancy in the form of MultiLink Trunking
 Silicon Switch Fabric redundancy and load-sharing
 Split Multi-Link Trunking (SMLT)
 Hot-swappable I/O modules
Chapter 2 Network management and diagnostics 41
Networking Concepts for the Passport 8000 Series Switch

 Router redundancy through VRRP
 Redundant fans and power supply units
 Basic CPU availability  warm standby
 High CPU availability  hot standby
You can protect against CPU failure by installing dual silicon switch fabric
(SSF)/CPU modules in a Passport 8000 Series chassis. In the event that the
primary SSF/CPU module fails, the backup SSF/CPU assumes the primary role.
You can configure CPU redundancy to provide either basic availability or high
availability.
In warm standby redundancy mode, if the primary CPU fails, the backup CPU
must initialize all input/output modules and load switch configurations, causing
delays and disrupting operations. In hot standby redundancy mode, both CPUs
maintain synchronized configuration and operational databases, enabling very
quick recovery and high availability.
If you enable layer 2 CPU redundancy you automatically disable layer 3 routing
operations on the switch and will be unable to configure routing parameters.
When you enable layer 2 CPU redundancy, both the primary and backup CPUs
synchronize their database structures following initialization. This process, which
takes a little time, need only be performed on initialization.
Network Time Protocol (NTP)
The Network Time Protocol (NTP) synchronizes the internal clocks of various
network devices across large, diverse networks to universal standard time. NTP
runs over UDP, which in turn runs over IP. The NTP protocol specification is
documented in RFC 1305.
Every network device relies on an internal system clock to maintain accurate time.
On local devices, the internal system clock is usually set by eye or by wristwatch
to within a minute or two of the actual time and is rarely reset at regular intervals.
Many local clocks are battery-backed devices that use room temperature clock
42 Chapter 2 Network management and diagnostics
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oscillators that can drift as much as several seconds each day. NTP solves this
problem by automatically adjusting the time of the devices so that they are
synchronized within a millisecond (ms) on LANs and up to a few tens of
milliseconds on WANs relative to Coordinated Universal Time (UTC).
The current implementation of NTP supports only unicast client mode. In this
mode, the NTP client, which is tailored to the limitations of the Real Time Clock
(RTC) on the CPU board (Dallas Semiconductors DS1307 series), sends NTP
time requests to other remote time servers in an asynchronous fashion. The NTP
client collects four samples of time from each remote time server. A clock
selection algorithm determines the best server among the selected samples based
on stratum, delay, dispersion and the last updated time of the remote server. The
RTC is adjusted to the selected sample from the chosen server.
NTP terms
A peer can be any device that runs NTP software. However, this implementation
of NTP refers to peers as remote time servers that provide time information to
other time servers on the network and to the local NTP client. An NTP client
refers to the local network device  in this case, a Passport 8000 Series switch 
that accepts time information from other remote time servers.
NTP system implementation model
NTP is based on a hierarchical model that consists of a local NTP client that runs
on the Passport 8000 Series switch and on remote time servers. The NTP client
requests and receives time information from one or more remote time servers. The
local NTP client reviews the time information from all available time servers and
synchronizes its internal clock to the time server whose time is most accurate. The
NTP client does not forward time information to other devices running NTP.
There are two types of time servers in the NTP model: primary time servers and
secondary time servers. A primary time server is directly synchronized to a
primary reference source, usually a wire or radio clock that is synchronized to a
radio station providing a standard time service. The primary time server is the
authoritative time source in the hierarchy, meaning that it is the one true time
source to which the other NTP devices in the subnet synchronize their internal
clocks.
Chapter 2 Network management and diagnostics 43
Networking Concepts for the Passport 8000 Series Switch

A secondary time server uses a primary time server or one or more secondary time
servers to synchronize its time, forming a synchronization subnet ( Figure 1). A
synchronization subnet is a self-organizing, hierarchical master-slave
configuration with the primary servers at the root and secondary servers of
decreasing accuracy at successive levels.
Figure 1 shows NTP time servers forming a synchronization subnet.
Figure 1 NTP time servers forming a synchronization subnet
In the NTP model, the synchronization subnet automatically reconfigures in a
hierarchical primary-secondary (master-slave) configuration to produce accurate
and reliable time, even if one or more primary time servers or the path between
them fails. This feature applies in a case in which all the primary servers on a
partitioned subnet fail, but one or more backup primary servers continue to
operate. If all of the primary time servers in the subnet fail, the remaining
secondary servers synchronize among themselves.
How NTP distributes time within a subnet
NTP distributes time through a hierarchy of primary and secondary servers, with
each server adopting a stratum (see Figure 1 on page 43). A stratum defines how
many NTP hops away a particular secondary time server is from an authoritative
time source (primary time server) in the synchronization subnet. A stratum 1
TCP0007A
P
S
S
S
C
C
Stratum 1
Stratum 2
Secondary
server
Client
Primary
server
44 Chapter 2 Network management and diagnostics
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time server is located at the top of the hierarchy and is directly attached to an
external time source, typically a wire or radio clock; a stratum 2 time server
receives its time via NTP from a stratum 1 time server; a stratum 3 time server
receives its time via NTP from a stratum 2 time server, and so forth.
Each NTP client in the synchronization subnet chooses as its time source the
server with the lowest stratum number with which it is configured to communicate
via NTP. This strategy effectively builds a self-organizing tree of NTP speakers.
The number of strata is limited to 15 to avoid long synchronization loops.
NTP tries not to synchronize to a remote time server whose time might not be
accurate. It avoids doing this in two ways. First, NTP never synchronizes to a
remote time server that is not itself synchronized. Second, NTP compares the
times reported by several remote time servers.
Synchronizing with the best available time server
Unlike other time synchronization protocols, NTP does not attempt to synchronize
the remote time servers internal clocks to each other. Rather, NTP synchronizes
the servers clocks to universal standard time, using the best available time
source and transmission paths to that time source.
NTP uses the following criteria to determine the time server whose time is best:
 The time server with the lowest stratum
 The time server closest in proximity to the primary time server (reduces
network delays)
 The time server offering the highest claimed precision
NTP prefers to have access to several (at least three) servers at the lower stratum
level, since it can apply an agreement algorithm to detect a problem on any part of
the time source.
NTP modes of operation
NTP uses unicast client mode to enable time servers and NTP clients to
communicate in the synchronization subnet. The Passport 8000 Series switch
supports only unicast client mode.
Chapter 2 Network management and diagnostics 45
Networking Concepts for the Passport 8000 Series Switch

When you configure a set of remote time servers (peers), NTP creates a list that
includes each time servers IP address. The NTP client uses this list to determine
which remote time servers to query for time information.
When the NTP client queries the remote time servers, they respond with various
timestamps, along with information about their clocks, such as stratum, precision,
and time reference (Figure 2). The NTP client reviews the list of responses from