Avaya IP, ARP, RARP, RIP, and OSPF User Manual

BayRS Version 15.1

Part No. 308627-15.1 Rev 00 October 2001

600 Technology Park Drive Billerica, MA 01821-4130

Configuring IP, ARP, RARP, RIP, and OSPF Services

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.

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Notwithstanding any other license agreement that may pertain to, or accompany the delivery of, this computer software, the rights of the United States Government regarding its use, reproduction, and disclosure are as set forth in the Commercial Computer Software-Restricted Rights clause at FAR 52.227-19.

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308627-15.1 Rev 00

Nortel Networks Inc. Software License Agreement

This Software License Agreement (“License Agreement”) is between you, the end-user (“Customer”) and Nortel Networks Corporation and its subsidiaries and affiliates (“Nortel Networks”). PLEASE READ THE FOLLOWING CAREFULLY. YOU MUST ACCEPT THESE LICENSE TERMS IN ORDER TO DOWNLOAD AND/OR USE THE SOFTWARE. USE OF THE SOFTWARE CONSTITUTES YOUR ACCEPTANCE OF THIS LICENSE AGREEMENT. If you do not accept these terms and conditions, return the Software, unused and in the original shipping container, within 30 days of purchase to obtain a credit for the full purchase price.

“Software” is owned or licensed by Nortel Networks, its parent or one of its subsidiaries or affiliates, and is copyrighted and licensed, not sold. Software consists of machine-readable instructions, its components, data, audio-visual content (such as images, text, recordings or pictures) and related licensed materials including all whole or partial copies. Nortel Networks grants you a license to use the Software only in the country where you acquired the Software. You obtain no rights other than those granted to you under this License Agreement. You are responsible for the selection of the Software and for the installation of, use of, and results obtained from the Software.

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iii

4. General

a. If Customer is the United States Government, the following paragraph shall apply: All Nortel Networks

Software available under this License Agreement is commercial computer software and commercial computer software documentation and, in the event Software is licensed for or on behalf of the United States Government, the respective rights to the software and software documentation are governed by Nortel Networks standard commercial license in accordance with U.S. Federal Regulations at 48 C.F.R. Sections

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308627-15.1 Rev 00

Preface

Before You Begin ............................................................................................................ xvii

Text Conventions ........................................................................................................... xviii

Acronyms .........................................................................................................................xix

Related Publications ........................................................................................................xxi

How to Get Help .............................................................................................................xxii

Chapter 1 IP Concepts, Terminology, and Features

IP Addresses .................................................................................................................. 1-2

Subnet Addressing ...................................................................................................1-4

Supernet Addressing ...............................................................................................1-7

Classless Interdomain Routing ................................................................................ 1-8

Autonomous Systems .....................................................................................................1-8

Addresses and Variable-Length Masks ........................................................................1-10

Address Resolution Protocol (ARP) .............................................................................1-10

Reverse Address Resolution Protocol (RARP) .............................................................1-13

Routing Information Protocol (RIP) ...............................................................................1-14

Open Shortest Path First (OSPF) Protocol ...................................................................1-14

OSPF Neighbors ....................................................................................................1-15

Neighbor Adjacencies ............................................................................................1-15

Designated Routers ...............................................................................................1-16

AS External Routes ................................................................................................1-16

OSPF Areas ...........................................................................................................1-17

Stub Area .........................................................................................................1-18

Not-So-Stubby Area (NSSA) ...........................................................................1-18

OSPF Router Types ...............................................................................................1-19

OSPF Implementation Notes .................................................................................1-19

Router Discovery Protocol ............................................................................................1-20

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Route Preferences ........................................................................................................ 1-21

Route Weights ..............................................................................................................1-22

IP Routing Policies and Filters ......................................................................................1-23

How OSPF Implements Routing Policies ...............................................................1-27

IP Traffic Filters .............................................................................................................1-28

Chapter 2 Starting IP Services

Using the BCC ................................................................................................................ 2-2

Starting IP ................................................................................................................2-2

Step 1: Configuring a Physical Interface ............................................................2-2

Step 2: Configuring an IP Interface ....................................................................2-3

Starting RIP ..............................................................................................................2-3

Starting OSPF ..........................................................................................................2-4

Starting Router Discovery ........................................................................................2-4

Using Site Manager ........................................................................................................2-5

Starting IP ................................................................................................................2-5

Starting RIP ..............................................................................................................2-6

Adding RIP to an IP Interface ............................................................................2-7

Starting OSPF ..........................................................................................................2-8

Starting RARP ..........................................................................................................2-9

Starting Router Discovery ......................................................................................2-10

Chapter 3 Configuring and Customizing IP

Customizing IP Global Parameters .................................................................................3-2

Disabling and Reenabling Global IP ........................................................................ 3-3

Configuring the Router for Not-Forwarding Mode .................................................... 3-4

Specifying Whether to Listen for RIP Packets in Host-Only Mode ..................... 3-5

Configuring Bridging on a Router in Not-Forwarding Mode ...............................3-6

Setting the Time-to-Live Value on a Source Packet ................................................. 3-9

Allowing an All-Zero or All-One Subnet Address ...................................................3-10

Estimating the Size of the Routing Table ................................................................3-11

Using a Default Route for Unknown Subnets .........................................................3-13

Specifying the Maximum Number of IP Policies .....................................................3-14

Setting the ICMP Error Limit .................................................................................. 3-15

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Disabling and Reenabling Route Filter Support .....................................................3-16

Configuring Equal-Cost Multipath Support for RIP and OSPF ...............................3-17

Enabling ISP Mode on the Router ..........................................................................3-20

Customizing the IP Routing Table Structure ..........................................................3-22

Specifying the Percentage of Buffers Available to ARP .........................................3-23

Enabling Directed Broadcast on a Router ..............................................................3-24

Blocking Source Record Routing ..................................................................................3-25

Customizing an IP Interface ..........................................................................................3-26

Disabling and Reenabling an IP Interface .............................................................. 3-29

Specifying a Broadcast Address for an Interface ...................................................3-30

Specifying the Cost of an Interface ........................................................................3-31

Enabling MTU Discovery on an Interface ...............................................................3-33

Enabling and Disabling ICMP Address-Mask Replies ............................................3-34

Disabling and Reenabling ICMP Redirect Messages .............................................3-36

Enabling All-Subnet Broadcasting on an Interface .................................................3-37

Disabling UDP Checksum Processing on an Interface ..........................................3-39

Specifying a MAC Address ....................................................................................3-40

Enabling Source Routing over a Token Ring Network ............................................3-41

Configuring the MTU for an IP Interface .................................................................3-44

Configuring an SMDS Address ..............................................................................3-45

Configuring a WAN Address for a Frame Relay Network .......................................3-46

Specifying the Maximum Size of the Forwarding Table ..........................................3-47

Deleting IP from an Interface .................................................................................3-49

Configuring the Circuitless IP Interface ........................................................................3-50

Choosing Slots to Support the Circuitless Interface ...............................................3-52

Configuring an Unnumbered IP Interface .....................................................................3-53

Creating an Unnumbered Interface ........................................................................ 3-55

Using the Alternate Associated Address Option ....................................................3-56

Configuring an Adjacent Host Address .........................................................................3-57

Defining a Static Route .................................................................................................3-60

Defining a Default Route ........................................................................................3-64

Defining a Static Black Hole for a Supernet ...........................................................3-64

Customizing Router Discovery .....................................................................................3-65

Enabling and Disabling Router Discovery .............................................................. 3-66

Choosing a Broadcast Type ...................................................................................3-67

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Specifying the Time Interval Between Advertisements ..........................................3-68

Configuring the Lifetime of Advertised Addresses ................................................. 3-69

Specifying Interface Preference .............................................................................3-70

Chapter 4 Customizing ARP and RARP Services

Customizing ARP ...........................................................................................................4-2

Disabling and Reenabling Global ARP .................................................................... 4-2

Customizing Global ARP ..........................................................................................4-3

Logging Nonlocal ARP Source Addresses ........................................................4-3

Setting the Nonlocal ARP Destination Response .............................................. 4-3

Selecting an Address Resolution Scheme for an IP Interface .................................. 4-5

Selecting an Encapsulation Option for ARP and Probe ...........................................4-8

Enabling Proxy ARP on an Interface ........................................................................4-9

Timing Out Entries in the Address Resolution Cache ............................................ 4-11

Customizing RARP .......................................................................................................4-13

Disabling and Reenabling RARP on an Interface ..................................................4-13

Defining the RARP Mapping Table .........................................................................4-14

Disabling and Reenabling RARP Globally .............................................................4-15

Deleting RARP Globally .........................................................................................4-16

Chapter 5 Customizing RIP Services

Setting the RIP Diameter ................................................................................................5-2

Customizing a RIP Interface ...........................................................................................5-3

Disabling and Reenabling RIP on an Interface ........................................................ 5-3

Selecting the RIP Version ........................................................................................5-4

Authenticating the Password on a Version 2 Update ................................................ 5-6

Supplying RIP Updates on an Interface ................................................................... 5-8

Specifying the Update Mode ....................................................................................5-9

Sending Triggered Updates ....................................................................................5-11

Specifying a Time-to-Live Value .............................................................................5-12

Receiving RIP Updates ..........................................................................................5-14

Supplying a Default Route on an Interface .............................................................5-15

Listening for a Default Route ..................................................................................5-17

Configuring a RIP Interface for Dial-Optimized Routing .........................................5-18

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Specifying the Full Update Interval ..................................................................5-18

Specifying a Timeout Period ............................................................................5-20

Specifying a Holddown Period .........................................................................5-21

Specifying a Stabilization Time ........................................................................5-22

Specifying Frame Relay Services for Adjacent Hosts ............................................5-23

Deleting RIP from an Interface ...............................................................................5-24

Configuring RIP Accept and Announce Policies ...........................................................5-25

Defining a RIP Accept Policy ..................................................................................5-26

Specifying Match Criteria for a RIP Accept Policy .................................................. 5-29

Supplying Modification Values for a RIP Accept Policy .......................................... 5-31

Defining a RIP Announce Policy ............................................................................ 5-32

Specifying Match Criteria for a RIP Announce Policy ............................................5-35

Supplying Modification Values for a RIP Announce Policy .....................................5-40

Chapter 6 Customizing OSPF Services

Customizing OSPF Global Parameters ..........................................................................6-2

Disabling and Reenabling OSPF on the Router .......................................................6-3

Supplying an OSPF Router ID .................................................................................6-4

Configuring the Soloist on a Slot ..............................................................................6-5

Configuring an OSPF Router as a Boundary Router ...............................................6-6

Configuring the Metric Type for an ASE Advertisement .....................................6-8

Choosing a Tag Generation Method for an ASE Advertisement ......................6-11

Setting the Holddown Timer ................................................................................... 6-14

Setting a Maximum Number of Refreshes for Summary and ASE LSAs ...............6-15

Configuring Message Logging ...............................................................................6-16

Configuring External Route Preference .................................................................6-18

Customizing OSPF on an IP Interface ..........................................................................6-19

Disabling and Reenabling OSPF on an Interface ...................................................6-20

Changing the Area ID .............................................................................................6-21

Specifying the Interface Type .................................................................................6-22

Specifying Router Priority for a Multiaccess Network ............................................6-24

Estimating the Transit Delay ...................................................................................6-26

Setting the Retransmit Interval ...............................................................................6-27

Setting the Hello Interval ........................................................................................6-28

Setting the Dead Interval .......................................................................................6-30

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Setting the Poll Interval for NBMA Neighbors ........................................................6-32

Specifying the Metric Cost .....................................................................................6-33

Specifying the MTU Size ........................................................................................6-35

Specifying the MTU Mismatch Detect ....................................................................6-37

Configuring a Neighbor on an NBMA Interface ......................................................6-38

Deleting OSPF from an IP Interface .......................................................................6-41

Configuring Areas .........................................................................................................6-42

Creating an Area ....................................................................................................6-42

Disabling and Reenabling an Area .........................................................................6-44

Configuring Authentication ..................................................................................... 6-45

Configuring a Summary Route ...............................................................................6-47

Configuring a Stub Area .........................................................................................6-49

Configuring a Not-So-Stubby Area (NSSA) ...........................................................6-51

Configuring an NSSA Address Range ..........................................................................6-55

Configuring an Area Border Router ..............................................................................6-58

Configuring a Virtual Link Through a Transit Area .................................................6-59

Configuring OSPF Accept and Announce Policies .......................................................6-64

Defining an OSPF Accept Policy ............................................................................6-65

Specifying Match Criteria for an OSPF Accept Policy ............................................6-68

Defining an OSPF Announce Policy .......................................................................6-70

Specifying Match Criteria for an OSPF Announce Policy .......................................6-72

Specifying Modification Values for an OSPF Announce Policy ..............................6-76

Appendix A Site Manager Parameters

IP Parameters ................................................................................................................ A-2

IP Configuration Parameters ................................................................................... A-2

IP Interface Parameters .......................................................................................... A-5

IP Global Parameters ............................................................................................ A-18

Static Route Parameters ....................................................................................... A-27

Adjacent Host Parameters .................................................................................... A-30

Router Discovery Parameters ............................................................................... A-33

RARP Parameters ....................................................................................................... A-35

OSPF Parameters ....................................................................................................... A-36

OSPF Global Parameters ...................................................................................... A-37

OSPF Interface Parameters .................................................................................. A-41

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Neighbor Parameters for an NBMA Interface ........................................................ A-47

OSPF Area Parameters ........................................................................................ A-49

Area Range Parameters ........................................................................................ A-53

OSPF NSSA Range Parameters ........................................................................... A-56

OSPF Virtual Interface Parameters ....................................................................... A-59

RIP Parameters ........................................................................................................... A-62

Accept and Announce Policy Parameters .................................................................... A-69

Common Accept Policy Parameters ...................................................................... A-70

RIP Accept Policy Parameters .............................................................................. A-73

OSPF Accept Policy Parameters ........................................................................... A-75

Common Announce Policy Parameters ................................................................. A-76

RIP Announce Policy Parameters ......................................................................... A-86

OSPF Announce Policy Parameters ..................................................................... A-87

Appendix B Import and Export Route Filters

RIP Import Filters .......................................................................................................... B-2

RIP Export Filters .......................................................................................................... B-5

OSPF Import Filters ....................................................................................................... B-8

OSPF Export Filters .................................................................................................... B-11

Appendix C Route Weight Worksheet

Appendix D IP/OSPF Configuration Example

Configuring Internal Backbone Router 1 ....................................................................... D-3

Configuring Area Border Router 2 ................................................................................. D-4

Configuring Area Border Router 3 ................................................................................. D-6

Configuring Area Border Router 4 ................................................................................. D-8

Configuring Internal Backbone Router 5 ..................................................................... D-10

Configuring AS Boundary Router 6 ............................................................................. D-11

Index

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Figures

Figure 1-1. Network and Host Portions of IP Addresses ............................................ 1-3

Figure 1-2. Supernet Addresses ................................................................................1-7

Figure 1-3. Internetwork Segmented into Three Autonomous Systems .....................1-9

Figure 1-4. ARP Example .........................................................................................1-11

Figure 1-5. RARP Server Supplying an IP Address .................................................1-13

Figure 1-6. OSPF Areas ........................................................................................... 1-17

Figure 1-7. IP Routing Table .....................................................................................1-24

Figure 1-8. Accept and Announce Policies ...............................................................1-26

Figure 3-1. IP Interface .............................................................................................3-27

Figure 3-2. IP Routers Source Routing Across a Token Ring Network ....................3-42

Figure 4-1. Proxy ARP Example ................................................................................4-9

Figure 6-1. OSPF ASE Routes ...................................................................................6-9

Figure 6-2. AS External Route Tag ...........................................................................6-12

Figure 6-3. Example of Using Configurable Cost Metrics ........................................6-33

Figure 6-4. Area Border Router ................................................................................ 6-58

Figure 6-5. Virtual Link and Transit Area ..................................................................6-60

Figure D-1. IP/OSPF Configuration ........................................................................... D-2

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Tables

Table 1-1. Network Classes and IP Addresses .........................................................1-2

Table 1-2. Subnet Masks for Class B and Class C Addresses .................................1-6

Table 3-1. Source Routing Bridge Support for Host-Only Mode ............................... 3-6

Table 3-2. Learning Bridge Support for Host-Only Mode ..........................................3-7

Table 3-3. MAC Address Parameter Settings .........................................................3-40

Table 3-4. BCC Adjacent Host Parameters .............................................................3-58

Table 3-5. Required BCC Static Route Parameters ................................................3-62

Table 3-6. Optional BCC Static Route Parameters .................................................3-62

Table 5-1. RIP Version Options .................................................................................5-5

Table 5-2. BCC Definition Parameters for RIP Accept Policies ...............................5-27

Table 5-3. BCC Match Parameters for RIP Accept Policies ....................................5-29

Table 5-4. BCC Definition Parameters for RIP Announce Policies .........................5-33

Table 5-5. BCC Match Parameters for RIP Announce Policies ...............................5-35

Table 5-6. BCC Modification Parameters for RIP Announce Policies .....................5-40

Table 6-1. OSPF Log Messages .............................................................................6-16

Table 6-2. OSPF Interface Types ............................................................................ 6-23

Table 6-3. OSPF Retransmit Interval Settings ........................................................6-27

Table 6-4. OSPF Hello Interval Settings .................................................................6-29

Table 6-5. OSPF Dead Interval Settings .................................................................6-30

Table 6-6. OSPF Metric Cost Settings (per RFC 2328) ..........................................6-34

Table 6-7. BCC Neighbor Parameters for an NBMA Interface ................................6-39

Table 6-8. BCC Parameters for OSPF NSSA .........................................................6-53

Table 6-9. BCC Address Range Parameters for OSPF NSSA ...............................6-56

Table 6-10. BCC Parameters for OSPF Virtual Link .................................................6-62

Table 6-11. BCC Definition Parameters for OSPF Accept Policies ...........................6-66

Table 6-12. BCC Match Parameters for OSPF Accept Policies ................................ 6-68

Table 6-13. BCC Definition Parameters for OSPF Announce Policies ......................6-71

Table 6-14. BCC Match Parameters for OSPF Announce

Policies 6-73

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Table 6-15. BCC Modification Parameters for OSPF Announce Policies ................. 6-76

Table D-1. Internal Backbone Router 1 .................................................................... D-3

Table D-2. Area Border Router 2 .............................................................................. D-4

Table D-3. Area Border Router 3 .............................................................................. D-6

Table D-4. Area Border Router 4 .............................................................................. D-8

Table D-5. Internal Backbone Router 5 .................................................................. D-10

Table D-6. AS Boundary Router 6 .......................................................................... D-11

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This guide describes Internet Protocol (IP) services and what you do to start and customize IP services on a Nortel Networks* router.

You can use the Bay Command Console (BCC*) or Site Manager to configure IP services on a router. In this guide, you will find instructions for using both the BCC and Site Manager.

Before You Begin

Before using this guide, you must complete the following procedures. For a new router:

Preface

• Install the router (see the installation guide that came with your router).

• Connect the router to the network and create a pilot configuration file (see

Make sure that you are running the latest version of Nortel Networks BayRS* and Site Manager software. For information about upgrading BayRS and Site Manager, see the upgrading guide for your version of BayRS.

308627-15.1 Rev 00

Quick-Starting Routers, Configuring BayStack Remote Access, or Connecting ASN Routers to a Network).

xvii

Configuring IP, ARP, RARP, RIP, and OSPF Services

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>

ping 192.32.10.12

, you enter:

bold text

Indicates command names and options and text that you need to enter.

Example: Enter

Example: Use the

show ip {alerts | routes

dinfo

command.

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 show ip alerts or show ip routes

}

, you must enter either:

, 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 show ip interfaces

]

, you can enter either:

show ip interfaces -alerts

ellipsis points (. . . ) Indicate that you repeat the last element of the

command as needed.

xviii

Example: If the command syntax is:

ethernet/2/1 ethernet/2/1

[<parameter> <value>]

and as many parameter-value pairs as

needed.

. . .

, you enter

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Preface

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.

screen text Indicates system output, for example, prompts and

system messages.

Acronyms

Example:

Set Trap Monitor Filters

separator ( > ) Shows menu paths.

Example: Protocols > IP identifies the IP option 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 show ip alerts

}

show ip routes

This guide uses the following acronyms:

ARE all routes explorer

ARP Address Resolution Protocol

AS autonomous system

, you enter either:

, but not both.

308627-15.1 Rev 00

ASB all-subnet broadcast

ASBR AS boundary router

ASE autonomous system external

ATM asynchronous transfer mode

xix

Configuring IP, ARP, RARP, RIP, and OSPF Services

BGP Border Gateway Protocol

BootP Bootstrap Protocol

BR border router

CIDR classless interdomain routing

DVMRP Distance Vector Multicast Routing Protocol

ECMP equal-cost multipath

EGP Exterior Gateway Protocol

FDDI Fiber Distributed Data Interface

FIFO first in first out

ICMP Internet Control Message Protocol

IGP interior gateway protocol

IP Internet Protocol

ISP Internet service provider

LIS logical IP subnet

LSA link state advertisement

LSDB link state database

MAC media access control

MOSPF Multicasting Open Shortest Path First

MTU maximum transmission unit

NBMA nonbroadcast multi-access

NIC Network Information Center

NSSA not-so-stubby area

OSPF Open Shortest Path First

PPP Point-to-Point Protocol

RARP Reverse Address Resolution Protocol

RFC Request for Comments

RIF routing information field

RIP Routing Information Protocol

SMDS Switched Multimegabit Data Service

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SNMP Simple Network Management Protocol

SRR source record route

STE spanning tree explorer

TTL time to live

UDP User Datagram Protocol

VC virtual circuit

WAN wide area network

Related Publications

For more information about IP services, refer to the following publications:

• Reference for BCC IP show Commands (part number 308603-14.20 Rev 00)

Provides descriptions of all commands that display IP, ARP, RIP, and OSPF configuration and statistical data.

show

commands for IP services, including the

Preface

• Configuring IP Exterior Gateway Protocols (BGP and EGP) (part number

• Configuring GRE, NAT, RIPSO, and BFE Services (part number

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.

308627-15.1 Rev 00

308628-15.0 Rev 00)

Provides a description of Border Gateway Protocol (BGP) and Exterior Gateway Protocol (EGP) services and instructions for configuring them.

308625-14.20 Rev 00)

Provides a description of Generic Routing Encapsulation (GRE), Network Address Translation (NAT), Revised IP Security Option (RIPSO), and Blacker front-end services and instructions for configuring them.

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Configuring IP, ARP, RARP, RIP, and OSPF Services

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

xxii

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.

308627-15.1 Rev 00

Chapter 1

IP Concepts, Terminology, and Features

This chapter introduces concepts and terminology used in this guide.

Topic Page

IP Addresses

Autonomous Systems 1-8

Addresses and Variable-Length Masks 1-10

Address Resolution Protocol (ARP) 1-10

Reverse Address Resolution Protocol (RARP) 1-13

Routing Information Protocol (RIP) 1-14

Open Shortest Path First (OSPF) Protocol 1-14

Router Discovery Protocol 1-20

Route Preferences 1-21

Route Weights 1-22

IP Routing Policies and Filters 1-23

IP Traffic Filters 1-28

1-2

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1-1

Configuring IP, ARP, RARP, RIP, and OSPF Services

IP Addresses

An IP address consists of 32 bits that have the form network.host. The network portion is a network number ranging from 8 to 24 bits. The host portion is the remaining 8 to 24 bits identifying a specific host on the network. The Internet Network Information Center (NIC) assigns the network portion of the IP address. Your network administrator assigns the host portion.

NIC recognizes three primary classes of networks: A, B, and C. In addition, NIC has recently identified two other classes: Class D for networks that support multicasting, which allows an IP datagram to be transmitted to a single multicast group consisting of hosts spread across separate physical networks; and Class E for experimental networks. The IP router does not fully support Class D or Class E networks.

Based on the size of the network, NIC classifies a network as Class A, B, or C (the most common). The network class determines the number of bits assigned to the network and host portions of the IP address (Tab le 1- 1

Table 1-1. Network Classes and IP Addresses

1-2

Network Size Class Network Portion Host Portion

More than 65,533 hosts A 8 bits 24 bits

254 to 65,533 hosts B 16 bits 16 bits

Fewer than 254 hosts C 24 bits 8 bits

The position of the first bit set to 0 (whether it is the first, second, third, or fourth bit) in the first octet of an IP address indicates the network class (A, B, C, or D). If no bit is set to 0, it is a Class E network. Figure 1-1

shows the placement of the first bit set to 0 for Class A, B, and C networks. The figure also shows how a network’s class affects the network and host portions of the IP address.

308627-15.1 Rev 00

IP Concepts, Terminology, and Features

8162431

Class A

Class B

Class C

Class A

Class B

Class C

8162431

101

First Octet Network Host

110

Network portion

Range

1-127

128-191

192-223

Host portion

Example

25.0.0.1

140.250.0.1

192.2.3.1

140.250

192.2.3

Figure 1-1. Network and Host Portions of IP Addresses

IP0005A

You specify IP addresses in dotted-decimal notation. To express an IP address in dotted-decimal notation, you convert each 8-bit octet of the IP address to a decimal number and separate the numbers by decimal points.

For example, you specify the 32-bit IP address 10000000 00100000 00001010 10100111 in dotted-decimal notation as 128.32.10.167. The most significant 2 bits (10) in the first octet indicate that the network is Class B; therefore, the first 16 bits compose the NIC-assigned network portion field. The third octet (00001010) and fourth octet (10100111) compose the host field.

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Configuring IP, ARP, RARP, RIP, and OSPF Services

Subnet Addressing

The concept of subnetworks (or subnets) extends the IP addressing scheme. Subnets are two or more physical networks that share a common network-identification field (the NIC-assigned network portion of the 32-bit IP address). Subnets allow an IP router to hide the complexity of multiple LANs from the rest of the internetwork.

Using subnets, you partition the host portion of an IP address into a subnet number and a “real” host number on that subnet. The IP address is then defined by network.subnet.host. Routers outside the network do not interpret the subnet and host portions of the IP address separately.

Routers within a network containing subnets use a 32-bit subnet mask that identifies the extension bits. In network.subnet.host, the subnet.host portion (or the local portion) contains an arbitrary number of bits. The network administrator allocates bits within the local portion to subnet and host, and then assigns values to subnet and host.

For example, the following is the IP address of a network that contains subnets: 10000000 00100000 00001010 10100111. You specify this address in dotted-decimal notation as 128.32.10.167.

1-4

The second bit of the first octet is set to 0, indicating that the network is a Class B network. Therefore, the NIC-assigned network portion contains 16 bits and the locally assigned local portion contains 16 bits.

The network administrator allocates the 16 bits in the local portion field as follows:

• Upper 8 bits (00001010) with a value of 10 to the subnet portion

• Lower 8 bits (10100111) with a value of 167 to the host portion

In other words, the 16-bit local portion field, together with the 16-bit network field, specify host 167 on subnet 10 of network 128.32.

You now need a subnet mask to identify those bits in the 32-bit IP address that specify the network field and those bits that specify the subnet field. Like the IP address, you specify the subnet mask in dotted-decimal notation.

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IP Concepts, Terminology, and Features

You construct a subnet mask as follows:

• Assign a value of 1 to each of the 8, 16, or 24 bits in the network field.

• Assign a value of 1 to each bit in the subnet field.

• Assign a value of 0 to each bit in the host field.

• Convert the resulting 32-bit string to dotted-decimal notation.

For example, to construct a subnet mask for the IP address 10000000 00100000 00001010 10100111, do the following:

1. Assign a value of 1 to each bit in the network field.

The position of the first bit set to 0 in the first octet of the IP address indicates that the network is Class B; therefore, the network field contains 16 bits: 11111111 11111111.

2. Assign a value of 1 to each bit in the subnet field.

Allocate the upper 8 bits of the local portion field to the subnet portion, as follows: 11111111.

3. Assign a value of 0 to each bit in the host field.

4. Convert the resulting 32-bit string (11111111 11111111 11111111 00000000)

308627-15.1 Rev 00

Allocate the lower 8 bits of the local portion field to the host identification, as follows: 00000000.

to dotted-decimal notation, as follows: 255.255.255.0.

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Configuring IP, ARP, RARP, RIP, and OSPF Services

Tabl e 1-2 lists the range of possible subnet masks for Class B and Class C

addresses, along with the number of bits that the mask allocates for a subnet address, the number of recommended subnets associated with the mask, and the number of hosts per subnet.

Table 1-2. Subnet Masks for Class B and Class C Addresses

Number of Subnets

Number of Bits Subnet Mask

Class B

2 255.255.192.0 2 16,382

3 255.255.224.0 6 8190

4 255.255.240.0 14 4094

5 255.255.248.0 30 2046

6 255.255.252.0 62 1022

7 255.255.254.0 126 510

8 255.255.255.0 254 254

9 255.255.255.128 510 126

10 255.255.255.192 1,022 62

11 255.255.255.224 2,046 30

12 255.255.255.240 4,094 14

13 255.255.255.248 8,190 6

14 255.255.255.252 16,382 2

Class C

2 255.255.255.192 2 62

3 255.255.255.224 6 30

4 255.255.255.240 14 14

5 255.255.255.248 30 6

6 255.255.255.252 62 2

(Recommended)

Number of Hosts per Subnet

1-6

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Supernet Addressing

A supernet is a group of networks identified by contiguous network addresses. Internet service providers (ISPs) can assign customers blocks of contiguous addresses to define supernets as needed.

Each supernet has a unique supernet address that consists of the upper bits shared by all addresses in the contiguous block. For example, Figure 1-2 block of contiguous 32-bit addresses (192.32.0.0 through 192.32.7.0 in dotted-decimal notation).

11000000 00100000 00000000 00000000 11000000 00100000 00000001 00000000 11000000 00100000 00000010 00000000 11000000 00100000 00000011 00000000 11000000 00100000 00000100 00000000 11000000 00100000 00000101 00000000

11000000 00100000 00000110 00000000 11000000 00100000 00000111 00000000

IP Concepts, Terminology, and Features

illustrates a

Figure 1-2. Supernet Addresses

The supernet address for this block is 11000000 00100000 00000, the 21 upper bits shared by the 32-bit addresses.

A complete supernet address consists of an address/mask pair:

• address is the first 32-bit IP address in the contiguous block. In this example,

• mask is a 32-bit string containing a set bit for each bit position in the supernet

The complete supernet address in this example is 192.32.0.0/255.255.248.0.

308627-15.1 Rev 00

IP0007A

the address is 11000000 00100000 00000000 00000000 (192.32.0.0 in dotted-decimal notation).

part of the address. The mask for the supernet address in this example is 11111111 11111111 11111000 00000000 (255.255.248.0 in dotted-decimal notation).

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Configuring IP, ARP, RARP, RIP, and OSPF Services

Classless Interdomain Routing

Classless interdomain routing (CIDR) is an addressing scheme that employs supernet addresses to represent multiple IP destinations. Rather than advertise a separate route for each destination in a supernet, a router can use a supernet address to advertise a single route — called an aggregate route — that represents all of the destinations. CIDR reduces the size of the routing tables used to store advertised IP routes.

OSPF supports classless routing within a domain.

Autonomous Systems

LANs and WANs interconnected by IP routers form a group of networks called an internetwork. For administrative purposes, an internetwork is divided into autonomous systems. An autonomous system (AS) is simply a collection of routers (called gateways in IP terminology) and hosts run by a single technical administrator that has a single, clearly defined routing policy. Each autonomous system has its own unique AS number assigned by the appropriate Internet Registry entity. Figure 1-3 autonomous systems.

depicts a sample internetwork segmented into three

1-8

308627-15.1 Rev 00

IP Concepts, Terminology, and Features

Autonomous

system 2

LAN

Router

LAN

Router

Autonomous

system 3

Router

LAN

Router

IP0006A

LAN

Router

Autonomous

system 1

LAN

Figure 1-3. Internetwork Segmented into Three Autonomous Systems

308627-15.1 Rev 00

1-9

Configuring IP, ARP, RARP, RIP, and OSPF Services

Addresses and Variable-Length Masks

A destination in a topology is expressed as an IP address and a variable-length mask. Together, the address and the mask indicate the range of destinations to which the route applies.

The ability to specify a range of networks allows the protocol to send one summary advertisement that represents multiple destinations. For example, a summary advertisement for the destination 128.185.0.0 with a mask of 0xffff0000 describes a single route to destinations 128.185.0.0 through 128.185.255.255. OSPF and BGP support variable-length masks. However, RIP advertises only the network address.

Address Resolution Protocol (ARP)

The IP router needs both a physical address and an IP address to transmit a datagram. If the router knows only the network host’s IP address, the Address Resolution Protocol (ARP) enables the router to determine the network host’s physical address by binding a 32-bit IP address to a 48-bit media access control (MAC) address. A router can use ARP across a single network only, and the network hardware must support physical broadcasts.

1-10

308627-15.1 Rev 00

IP Concepts, Terminology, and Features

For example, in Figure 1-4, the router and host C are on the same physical network. Both devices have an assigned IP address (the router’s is 140.250.200.1 and host C’s is 140.250.200.4), and both devices have an assigned physical address (the router’s is 00 00 A2 00 00 01 and host C’s is 00 00 A2 00 10 40).

140.250.200.0

Host

140.250.200.2

00 00A2 00 10 20

140.250.200.3

00 00A2 00 10 30

Figure 1-4. ARP Example

Host

Router

140.250.200.1 00 00A2 00 00 01

Host

140.250.200.4

00 00A2 00 10 40

IP0010A

308627-15.1 Rev 00

1-11

Configuring IP, ARP, RARP, RIP, and OSPF Services

In Figure 1-4, the router wants to send a packet to host C but knows only host C’s IP address. The router uses ARP to determine host C’s physical address, as follows:

1. The router broadcasts a special packet, called an ARP request, that asks IP

address 140.250.200.4 to respond with its physical address.

2. All network hosts receive the broadcast request.

3. Only host C responds with its hardware address.

The router maps host C’s IP address (140.250.200.4) to its physical address (00 00 A2 00 10 40) and saves the results in an address-resolution cache for future use.

The router can send ARP requests even if ARP, which is a dynamically loaded module, is not currently loaded on the router. To ensure that ARP is loaded correctly on a slot using Site Manager, choose Events Manager > Options > Filters; then select LOADER and Debug, and choose File > Get Current Log File. Verify that ARP is loaded on a slot by locating the following message in the log:

#xx:01/01/99 10:10:55.00 DEBUG SLOT x LOADERCODE:33 Loader service completed for ARP.EXE 0xxxxxxxxx

1-12

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IP Concepts, Terminology, and Features

Reverse Address Resolution Protocol (RARP)

You can configure a Nortel Networks router as a Reverse Address Resolution Protocol (RARP) server. A RARP server supplies clients on the same physical or logical LAN with IP addresses (Figure 1-5)

RARP request: What is my IP address?

RARP response: 192.32.2.23

Router (RARP server)

Server

SNM0007A

308627-15.1 Rev 00

Figure 1-5. RARP Server Supplying an IP Address

To use RARP services, you must set up a MAC address-to-IP address mapping table. This table lists the MAC addresses of clients and the corresponding IP addresses that the RARP server assigns to those clients. When a client needs to acquire an IP address, the following exchange takes place:

1. The client broadcasts a RARP request specifying its MAC address.

2. Upon receiving a RARP request, the router refers to its MAC address-to-IP address mapping table, then sends the client a response packet containing the corresponding IP address.

3. The client examines the response packet to learn its IP address.

You can configure RARP support on Ethernet, token ring, and Fiber Distributed Data Interface (FDDI) interfaces.

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Configuring IP, ARP, RARP, RIP, and OSPF Services

Routing Information Protocol (RIP)

The Routing Information Protocol (RIP) is a distance-vector protocol that enables routers in the same autonomous system to exchange routing information by means of periodic RIP updates. Routers transmit their own RIP updates to neighboring networks and listen for RIP updates from the routers on those neighboring networks. Routers use the information in the RIP updates to keep their internal routing tables current. For RIP, the “best” path to a destination is the shortest path (the path with the fewest hops). RIP computes distance as a metric, usually the number of hops (or routers) from the source network to the target network.

Open Shortest Path First (OSPF) Protocol

The Open Shortest Path First (OSPF) protocol is an interior gateway protocol (IGP) intended for use in large networks. Using a link state algorithm, OSPF exchanges topology information between routers in an autonomous system. Routers synchronize their topological databases. After the routers are synchronized and the routing tables are built, the routers flood topology information only in response to some topological change. For OSPF, the “best” path to a destination is the path that offers the least cost metric. In OSPF, cost metrics are configurable, allowing you to specify preferred paths.

1-14

OSPF is a link state protocol. When the state of the interface to each of the neighboring routers changes, a router running a link state protocol tests the status of the physical connection and sends this information to the other neighbors. A link state protocol does not require each router to send its entire routing table to its neighbors. Instead, each OSPF router floods only link state change information throughout the autonomous system (or area, if the AS is divided into areas). This process is referred to as the synchronization of the routers’ topological databases.

With the link state information, each router builds a shortest-path tree with itself as the root of the tree. It can then identify the shortest path from itself to each destination and build its routing table.

OSPF supports CIDR and can carry supernet advertisements within a routing domain.

308627-15.1 Rev 00

OSPF Neighbors

OSPF neighbors are any two routers that have an interface to the same network. In each OSPF network, routers use the Hello protocol to discover their neighbors and maintain neighbor relationships called adjacencies. On a broadcast or point-to-point network, the Hello protocol dynamically discovers neighbors; however, on a nonbroadcast multi-access network, you must manually configure neighbors.

The Hello protocol ensures that communication between neighbors is bidirectional. Periodically, OSPF routers send out Hello packets over all interfaces. Included in these Hello packets is the following information:

• The router’s priority

• The router’s Hello timer and dead timer values

• A list of routers that have sent Hello packets to this router on this interface

• The router’s choice for designated router and backup designated router

Bidirectional communication is verified when one router sees itself listed in the neighbor’s Hello packet.

IP Concepts, Terminology, and Features

Neighbor Adjacencies

Neighbors can form an adjacency for exchanging link state information. When two routers form a full adjacency, they go through a process called database exchange to synchronize their topological databases. When their databases are synchronized, the routers are said to be fully adjacent. From this point on, only link state information is passed between the routers, thus conserving bandwidth.

Routers connected by a point-to-point network always form an adjacency. Also, every router on a multiaccess network forms an adjacency relationship with the designated router and the backup designated router.

308627-15.1 Rev 00

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Configuring IP, ARP, RARP, RIP, and OSPF Services

Designated Routers

To further reduce the amount of routing traffic, the Hello protocol elects a designated router and a backup designated router on each multiaccess broadcast network. Instead of neighboring routers forming adjacencies and exchanging link state information with each other (which on a large network can mean a lot of routing protocol traffic), all routers on the network form adjacencies with the designated router and the backup designated router only and send link state information to them. The designated router then redistributes the information from each router to every other router.

The Hello protocol always elects a backup designated router along with the designated router. The backup designated router takes over all of the designated router’s functions should the designated router fail.

AS External Routes

OSPF considers the following routes to be AS external (ASE) routes:

• Static route (host, network, or default)

• Route derived by RIP or BGP

1-16

• Directly connected network not running OSPF

In Figure 1-6 to connect the backbone to external ASs. R7 in area 0.0.0.1 and R15 in area

0.0.0.3 are also boundary routers that use RIP to connect to external ASs. R19 in area 0.0.0.4 connects the area to an external AS via BGP.

, for example, routers R1 and R2 are boundary routers that use BGP

308627-15.1 Rev 00

OSPF Areas

IP Concepts, Terminology, and Features

OSPF routers reduce and restrict the amount of internal and external link state information that is flooded through the AS by dividing the AS into areas.

Figure 1-6

shows an OSPF autonomous system divided into four areas and a required central area called a backbone that is used to distribute link state information among areas.

BGP BGP

Backbone

area 0.0.0.0

Area

0.0.0.1

RIP

R10

Stub area 0.0.0.2

Figure 1-6. OSPF Areas

R13

NSSA

0.0.0.3

R11

R15

R16

R12

R17

R14

R18

RIP

R19

BGP

Area 0.0.0.4

IP0048A

308627-15.1 Rev 00

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Configuring IP, ARP, RARP, RIP, and OSPF Services

Each area has a unique ID number. (ID 0.0.0.0 is always reserved for the OSPF backbone.) The AS in Figure 1-6

has the following four areas:

• Backbone area: 0.0.0.0

• Normal areas: 0.0.0.1 and 0.0.0.4

• Stub area: 0.0.0.2

• Not-so-stubby area (NSSA): 0.0.0.3

For information about associating an OSPF interface with an area ID, see

Changing the Area ID” on page 6-21.

“

Stub Area

A stub area does not import AS external routes and may or may not import internal route summaries. In place of routes to destinations outside the stub area, a border router connected to a stub (R8 in Figure 1-6 advertisement. When an internal router encounters a datagram addressed to a destination outside the stub area, the router forwards it to the border router specified in the default route advertisement.

) injects a default route

1-18

Not-So-Stubby Area (NSSA)

A not-so-stubby area (NSSA) is similar to a stub area except that, to a limited degree, an NSSA can import AS external routes. Like a stub area, an NSSA consumes less memory and CPU resources by preventing the flooding of type 5 AS external link state advertisements (LSAs) into the area and by relying on default routing to external destinations. However, unlike a stub area, an NSSA can import external routes into an OSPF routing domain. You can also configure type 7 address ranges to allow NSSA border routers to control the summarization of external routes for the NSSA.

308627-15.1 Rev 00

OSPF Router Types

OSPF defines the following router types:

• Internal router. A router with interfaces to networks in one area only. Internal

routers flood each area with complete routing information about changes that occur within the area. In Figure 1-6 internal routers.

• Border router. A router with an interface to the backbone network and

interfaces to one or more additional areas. Each border router connects one or more areas to the backbone. In Figure 1-6 routers. Using the backbone, border routers ensure that AS external (ASE) routes and summaries of routing information for all areas are distributed throughout the AS.

• Boundary router. A router configured to import non-OSPF routes and to inject

this information into an OSPF AS. In Figure 1-6 are boundary routers.

OSPF Implementation Notes

IP Concepts, Terminology, and Features

, R4, R5, and R6 in area 0.0.0.1 are

, R3, R8, R11, and R16 are border

, R1, R2, R7, R15, and R19

This section provides suggestions to help you configure your OSPF network. The Nortel Networks implementation of OSPF does not restrict you to these suggestions, but we provide them as guidelines.

• Use the same password throughout an area, or even throughout the entire

• Use the default timer values if possible. However, if you have any devices in

• Use address ranges if your network is a subnetted network.

• Keep all subnets within one area.

• Make sure that the AS boundary router function is enabled if the router has

• Every area border router must have a configured interface (physical or virtual)

308627-15.1 Rev 00

OSPF AS, if possible.

your network running OSPF, and you are now adding a Nortel Networks router, ensure that the router’s OSPF interface timer values coincide with the timer values on the other routers’ OSPF interfaces attached to the same subnets.

any non-OSPF route sources and if you want the router to propagate that information into the OSPF domain.

to the backbone.

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Configuring IP, ARP, RARP, RIP, and OSPF Services

• OSPF considers the cost of a path, not the hop count, when choosing the best

path. Each interface, however, is assigned the default cost 1 for the path to which it interfaces. If you have a preferred path, you must change the metric cost for your interfaces. Assign a higher metric cost to those paths that are the least preferred paths.

• If BGP is also configured on the router, the OSPF and BGP router IDs must be

set to the same IP address.

• If you change the topology (for example, if you add an area, combine two

areas, or move routers), you must reconfigure the appropriate OSPF elements (OSPF area ranges/interfaces/neighbors/virtual links, and so on).

Router Discovery Protocol

Before a host can send IP datagrams beyond its directly attached subnet, the host must discover the address of at least one operational router on that subnet. Router Discovery is an extension of the Internet Control Message Protocol (ICMP) that enables hosts attached to multicast or broadcast networks to discover the IP addresses of their neighboring routers.

1-20

Routers configured with Router Discovery periodically multicast or broadcast a route advertisement from each of their interfaces, announcing the IP address or addresses of that interface. Hosts discover the addresses of their neighboring routers by listening for these advertisements. Hosts will use the router with the highest preference level as a gateway.

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Route Preferences

The IP router maintains an internal routing table. When determining how to forward a datagram, the IP router consults the table to determine the specific route that a datagram should take. A routing table can contain direct routes for the IP router’s network interfaces, static routes, and any routes learned from RIP, OSPF, BGP, or EGP. (Information about adjacent hosts is maintained in a separate table.)

Preferences determine what goes into the routing table. Multiple routes to the same destination may exist in the table. Preference values range from 1 (lowest) through 16 (highest).

By default, RIP, BGP, EGP, and OSPF external routes have a preference value of

1. Static routes, direct routes, and OSPF intra-area and interarea routes have a default preference value of 16.

You can configure a preference value from 1 through 16 for RIP, BGP, EGP, OSPF external, and static routes. You cannot configure a preference value for direct routes and OSPF intra-area and interarea routes.

IP Concepts, Terminology, and Features

To assign a preference value to a route learned by RIP, OSPF, BGP, or EGP, you configure an accept policy for the route (see “

IP Routing Policies and Filters” on page 1-23). If an incoming route matches the policy, IP assigns the preference

value that you specify to the route and considers the route for possible inclusion in the routing table.

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Configuring IP, ARP, RARP, RIP, and OSPF Services

Route Weights

Route weight calculation is an internal tool that IP uses to facilitate the selection of the best route among alternative routes to the same destination. Route-selection criteria are encoded into the route weight in a way that allows IP to compare routes simply by comparing their weight values, regardless of route sources.

Appendix C

contains a worksheet that you can use to calculate route weights in

your configuration.

Route weight calculation increases the efficiency of the route selection process. It also reduces the size of the routing database because all route selection parameters for each route are encoded in a single integer — the weight value — rather than stored in separate variables.

Using selection criteria encoded in the route weight, IP chooses routes in the following order:

1. The route with the highest preference value (see “Route Preferences” on page

1-21)

2. A direct route with the lowest metric

3. An OSPF intra-area route with the lowest metric

4. An OSPF interarea route with the lowest metric

5. An OSPF type 1 external route with the lowest metric

6. An OSPF type 2 external route with ASE metric support enabled

7. A BGP route with the highest LOCAL_PREF value

8. A RIP route with the lowest metric

1-22

9. An EGP route with the lowest metric

10. A static route with the lowest metric

Note:

If OSPF is configured to propagate external routes using the route weight as the type 2 metric, routes that are received as OSPF ASE type 2 routes are evaluated according to their respective origins (for example, RIP or BGP).

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IP Routing Policies and Filters

The IP router allows you to control the flow of routing data to and from the routing tables. This control is provided by two mechanisms:

• Accept and announce policies

• Import and export route filters

Note:

Accept and announce policies provide a superset of the parameters provided by import and export route filters. Nortel Networks supports both IP policies and IP route filters. However, if you are using import and export filters for routing table management, you should migrate as soon as possible to IP policies.

Every IP router maintains a table of current routing information. The routing table manager receives routing updates from the network through the IP routing protocols running on the router. Periodically, the routing table manager issues routing updates through the protocols.

IP Concepts, Terminology, and Features

Figure 1-7

shows a router configured with all the IP routing protocols supported by BayRS: OSPF, RIP, BGP-3, BGP-4, and EGP. The arrows indicate the direction of flow of routing information between the network and the protocols running on the router, between the protocols and the routing table manager, and between the routing table manager and the routing table.

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Configuring IP, ARP, RARP, RIP, and OSPF Services

IP network

OSPF

RIP BGP-3 BGP-4 EGP

manager

Routing table

Figure 1-7. IP Routing Table

Routing

table

IP0035A

1-24

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IP Concepts, Terminology, and Features

The flow of routing information between the network, the protocols, and the routing table manager is controlled by routing information policies.

Accept policies (and the subset of parameters provided by import filters) govern the addition of new routes (derived from RIP, OSPF, BGP, or EGP) to the routing tables. When RIP, OSPF, BGP, or EGP receives a new routing update, it consults its accept policies to validate the information before entering the update into the routing tables. Accept policies contain search information (to match fields in incoming routing updates) and action information (to specify the action to take with matching routes). If routes match the network list in the policy, then the specified policy action is performed.

Announce policies (and the subset of parameters provided by export filters) govern the propagation of RIP, OSPF, BGP, or EGP routing information. When preparing a routing advertisement, RIP, OSPF, BGP, or EGP consults its announce policies to determine whether the routes to specific networks are to be advertised and how they are to be propagated. Announce policies contain network numbers (to associate a policy with a specific network) and action information (to specify a route propagation procedure). If routes match the network list in the policy, then the specified policy action is performed.

For information about BGP and EGP, see Configuring IP Exterior Gateway Protocols (BGP and EGP).

Each time that a routing update arrives from a remote router, the following steps occur (Figure 1-8

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The protocol receiving the route consults an accept policy to determine whether to forward the route to the IP routing table manager or drop the route.

If the protocol forwards the route, the routing table manager determines whether to inject the route into the routing table.

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Configuring IP, ARP, RARP, RIP, and OSPF Services

policy

Routing

table

manager

Routing

table

Announce

policy

Figure 1-8. Accept and Announce Policies

IP0036A

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IP Concepts, Terminology, and Features

The routing protocol announces routes to other routers in the network as follows:

The routing table manager forwards a route for advertisement to the protocol.

The protocol consults an announce policy to determine whether or not to advertise the route to the network.

For instructions on configuring RIP policies, see “

Announce Policies” on page 5-25.

For descriptions of IP import and export filter parameters, see Appendix B

How OSPF Implements Routing Policies

OSPF applies accept and announce policies to routing information in several different ways from the procedure shown in Figure 1-7. OSPF link state advertisements (LSAs) are received and placed in the link state database (LSDB) of the router. The information in the LSDB is also propagated to other routers in the OSPF routing domain.

According to the OSPF standard, all routers in a given area must maintain a synchronized database. To maintain database integrity across the network, a router must not manipulate received LSAs before propagating them to other routers. To accomplish this, OSPF accept and announce policies act in the following manner:

• OSPF accept policies control which OSPF non-self-originated external

routing information is passed to the routing table manager. The accept policies control only what the local router uses; they do not affect the propagation of external information, AS external routes, or type 7 LSAs to other routers.

• OSPF announce policies control which non-OSPF routes to advertise into the

OSPF domain. These routes are advertised in AS external routes or type 7 LSAs.

Configuring RIP Accept and

For instructions on configuring OSPF policies, see “

and Announce Policies” on page 6-64.

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Configuring OSPF Accept

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Configuring IP, ARP, RARP, RIP, and OSPF Services

IP Traffic Filters

A traffic filter enables the router to selectively relay or drop an inbound packet, frame, or datagram based on standard protocol fields or user-defined fields. Traffic filters apply to incoming traffic only.

For information about IP traffic filters, see Configuring Traffic Filters and

Protocol Prioritization.

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Chapter 2

Starting IP Services

This chapter describes how to use the BCC and Site Manager to create a basic configuration — that is, a configuration using all available defaults — for the IP services described in this guide.

Topic Page

Using the BCC

Using Site Manager 2-5

2-2

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Using the BCC

You can use the BCC to start IP, RIP, OSPF, and Router Discovery. The following sections provide instructions for starting these services.

Topic Page

Starting IP

Starting RIP 2-3

Starting OSPF 2-4

Starting Router Discovery 2-4

2-2

To start IP on the router, you must:

1. Configure a physical interface on an available slot/connector.

2. Configure an IP interface on the physical interface.

Step 1: Configuring a Physical Interface

To configure a physical interface on a slot and connector, go to the top-level box or stack prompt and enter:

<interface_type> <connector_number>

interface_type

slot

is the name of a link module on the router.

<slot_number>

module

[

<module_number>

connector

]

2-2

slot_number

module_number

is the number of the slot on which the link or net module is located.

is the net module number (ASN* and System 5000* routers

only).

connector_number

is the number of a connector on the link or net module.

For example, the following command configures an Ethernet interface on slot 2, connector 2:

ethernet slot 2 connector 2

box# ethernet/2/2#

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Starting IP Services

Step 2: Configuring an IP Interface

To configure an IP interface on a physical interface, go to the prompt for the physical interface and enter:

Starting RIP

ip address

address

and

address>

mask

are a valid IP address and its associated mask, expressed in

mask

<mask>

dotted-decimal notation. (You can also enter the mask value as a decimal integer that represents the number of mask bits that make up the network portion of the IP address. For example, “8” equals the mask value “255.0.0.0.”)

For example, the following command configures IP interface 2.2.2.2/255.0.0.0 on an Ethernet physical interface on slot 2, connector 2:

ethernet/2/2# ip/2.2.2.2/255.0.0.0#

ip address 2.2.2.2 mask 255.0.0.0

An IP interface is now configured on the Ethernet interface with default values for all interface parameters. When you configure an IP interface, the BCC also configures IP globally on the router with default values for all IP global parameters.

You customize IP by modifying IP global and interface parameters as described in

Chapter 3, “

Configuring and Customizing IP.”

You start RIP on the router by adding RIP to an existing IP interface.

To start RIP, go to an IP interface prompt and enter:

rip

For example, the following command adds RIP to IP interface 2.2.2.2/255.0.0.0:

ip/2.2.2.2/255.0.0.0# rip/2.2.2.2#

RIP is now running on the router and on the interface with default values for all parameters. You customize RIP by modifying RIP parameters as described in

Chapter 5, “

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rip

Customizing RIP Services.”

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Configuring IP, ARP, RARP, RIP, and OSPF Services

Starting OSPF

You start OSPF on the router by adding OSPF to an existing IP interface.

To start OSPF, go to an IP interface prompt and enter:

ospf area

area_id

<area_id>

is the identifier, expressed in dotted-decimal notation, of the OSPF area to

which the router is connected through the IP interface.

For example, the following command adds OSPF to IP interface 2.3.3.3/255.0.0.0. This interface connects the router to OSPF area 0.0.0.0, the OSPF backbone.

ip/2.3.3.3/255.0.0.0# ospf/2.3.3.3#

OSPF is now running on the router and on the interface with default values for all parameters. You customize OSPF by modifying OSPF parameters as described in

Chapter 6, “

Customizing OSPF Services.”

Starting Router Discovery

You start Router Discovery by adding it to an IP interface.

To start Router Discovery, go to an IP interface prompt and enter:

rdisc

For example, the following command adds Router Discovery to IP interface

2.2.2.2/255.0.0.0:

ospf area 0.0.0.0

2-4

ip/2.2.2.2/255.0.0.0# rdisc/2.2.2.2#

rdisc

Router Discovery is now running on IP interface 2.2.2.2/255.0.0.0 with default values for all parameters. You customize Router Discovery by modifying parameters as described in “Customizing Router Discovery” on page 3-65.

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