Nortel Networks NN47200-503 User Manual

Nortel Ethernet Routing Switch 5500 Series

Conﬁguration-IP Routing Protocols

NN47200-503 (217465-C)

Document status: Standard Document version: 03.01 Document date: 27 August 2007

The information in this document is subject to change without notice. The statements, conﬁgurations, technical data, and recommendations in this document a re 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 .

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.

Restricted rights legend

Use, duplication, or disclosure by the United States Government is subject to restrictions as set forth in subparagraph (c)(1)(ii) of the Rights in Technical Data and Computer Software clause at DFARS 252.227-7013.

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.

Statement of conditions

In the interest of improving internal design, operational function, and/or reliability, Nortel Networks reserves the right to make changes to the products described in this document without notice.

Nortel Networks does not assume any liability that may occur due to the use or application of the product(s) or circuit layout(s) described herein.

Nortel Networks 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.

1. Licensed Use of Software. Nortel Networks grants Customer a nonexclusive license to use a copy of the Software on only one machine at any one time or to the extent of the activation or authorized usage level, whichever is applicable. To the extent Software is furnished for use with designated hardware or Customer furnished equipment ("CFE"), Customer is granted a nonexclusive license to use Software only on such hardware or CFE, as applicable. Software contains trade secrets and Customer agrees to treat Software as conﬁdential information using the same care and discretion Customer uses with its own similar information that it does not wish to disclose, publish or disseminate. Customer will ensure that anyone who uses the Software does so only in compliance with the terms of this Agreement. Customer shall not a) use, copy, modify, transfer or distribute the Software except as expressly authorized; b) reverse assemble, reverse compile, reverse engineer or otherwise translate the Software; c) create derivative works or modiﬁcations unless expressly authorized; or d) sublicense, rent or lease the Software. Licensors of intellectual property to Nortel Networks are beneﬁciaries of this provision. Upon termination or breach of the license by Customer or in the event designated hardware or CFE is no longer in use, Customer will promptly return the Software to Nortel Networks or certify its destruction. Nortel Networks may audit by remote polling or other

reasonable means to determine Customer’s Software activation or usage levels. If suppliers of third party software included in Software require Nortel Networks to include additional or different terms, Customer agrees to abide by such terms provided by Nortel Networks with respect to such third party software.

2. Warranty. Except as may be otherwise expressly agreed to in writing between Nortel Networks and Customer, Software is provided "AS IS" without any warranties (conditions) of any kind. NORTEL NETWORKS DISCLAIMS ALL WARRANTIES (CONDITIONS) FOR THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE AND ANY WARRANTY OF NON-INFRINGEMENT.Nortel Networks is not obligated to provide support of any kind for the Software. Some jurisdictions do not allow exclusion of implied warranties, and, in such event, the above exclusions may not apply.

3. Limitation of Remedies. IN NO EVENT SHALL NORTEL NETWORKS OR ITS AGENTS OR SUPPLIERS BE LIABLE FOR ANY OF THE FOLLOWING: a) DAMAGES BASED ON ANY THIRD PARTY CLAIM; b) LOSS OF, OR DAMAGE TO, CUSTOMER’S RECORDS, FILES OR DATA; OR c) DIRECT, INDIRECT, SPECIAL, INCIDENTAL, PUNITIVE, OR CONSEQUENTIAL DAMAGES (INCLUDING LOST PROFITS OR SAVINGS), WHETHER IN CONTRACT, TORT OR OTHERWISE (INCLUDING NEGLIGENCE) ARISING OUT OF YOUR USE OF THE SOFTWARE, EVEN IF NORTEL NETWORKS, ITS AGENTS OR SUPPLIERS HAVE BEEN ADVISED OF THEIR POSSIBILITY. The forgoing limitations of remedies also apply to any developer and/or supplier of the Software. Such developer and/or supplier is an intended beneﬁciary of this Section. Some jurisdictions do not allow these limitations or exclusions and, in such event, they may not apply.

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 12.212 (for non-DoD entities) and 48 C.F.R.

227.7202 (for DoD entities).

b) Customer may terminate the license at any time. Nortel Networks may terminate the license if Customer fails to comply with the terms and conditions of this license. In either event, upon termination, Customer must either return the Software to Nortel Networks or certify its destruction.

c) Customer is responsible for payment of any taxes, including personal property taxes, resulting from Customer’s use of the Software. Customer agrees to comply with all applicable laws including all applicable export and import laws and regulations.

d) Neither party may bring an action, regardless of form, more than two years after the cause of the action arose.

e) The terms and conditions of this License Agreement form the complete and exclusive agreement between

Customer and Nortel Networks.

f) This License Agreement is governed by the laws of the country in which Customer acquires the Software. If the Software is acquired in the United States, then this License Agreement is governed by the laws of the state of New York.

Revision History

Date Revised Version Reason for revision

July 2005

1.00

New document for Software Release 4.2.

July 2006 August 2007 3

2.00 .01 u

Document updated for Software Release 5.0.

pdated for Software Release 5.1

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6 Revision History

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Preface 9

Nortel Ethernet Routing Switch 5500 Series 9 Related publications 10 Finding the latest updates on the Nortel web site 11 How to get help 12

An Introduction to IP Routing Protocols 13

IP routing 13

IP addressing 13 IP routing using VLANs 16 Brouter port 19 Management VLAN 20 Setting IP routing 20 Address Resolution Protocol (ARP) 21 Static routes 22 Non-local static routes 23 Routing Information Protocol (RIP) 23 Open Shortest Path First (OSPF) protocol 27 Route policies 35 Virtual Router Redundancy Protocol (VRRP) 37 Equal Cost MultiPath (ECMP) 38 UDP broadcast forwarding 38 Dynamic Host Conﬁguration Protocol (DHCP) / Bootstrap Protocol (BootP) 39 Avoiding duplicate IP addresses 44 IP blocking 45

IGMP snooping 46

IGMP snooping conﬁguration rules 49

IP Routing Conﬁguration and Management 51

IP routing initial conﬁguration 51

Global IP routing conﬁguration 51 Open Shortest Path First (OSPF) initial conﬁguration 52

IP routing conﬁguration using the CLI 55

IP conﬁguration commands 55 Layer 3 routable VLANs 56

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8 Contents

Static route commands 59 Address Resolution Protocol (ARP) commands 64 Proxy ARP commands 66 Routing Information Protocol (RIP) commands 67 Open Shortest Path First (OSPF) commands 82 Route policy commands 101 Virtual Router Redundancy Protocol (VRRP) commands 104 Equal Cost MultiPath (ECMP) commands 110 Brouter port commands 112 UDP broadcast forwarding commands 113 DHCP relay commands 115

IP routing conﬁguration examples 120

Address Resolution Protocol (ARP) conﬁguration 120 Routing Information Protocol (RIP) conﬁguration 122 Open Shortest Path First (OSPF) conﬁguration 134 Virtual Router Redundancy Protocol (VRRP) conﬁguration 190 Equal Cost Multipath (ECMP) 204

IP routing conﬁguration using the Java Device Manager 206

Layer 3 routable VLANs 206 IP routing 209 Routing Information Protocol (RIP) conﬁguration 222 Open Shortest Path First (OSPF) conﬁguration 228 Route policies 264 Virtual Router Redundancy Protocol (VRRP) 277 Equal Cost MultiPath (ECMP) 284 Brouter port 285 UDP broadcast forwarding 288 UDP broadcast interface deletion 295 DHCP conﬁguration 295

Conﬁguring IGMP snooping using the Java Device Manager 305 Conﬁguring IGMP using Web-based management 309

Conﬁguring IGMP using the Web-based Management Interface 309 Displayingmulticastmembershipusing the Web-based Management Interface 312

Index 314

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Preface

This document provides information and instructions on the conﬁguration of IP Routing on the 5500 Series Nortel Ethernet Routing Switch. Consult any documentation included with the switch and the product release notes (see "Related publications" (page 10)) for any errata before beginning the conﬁguration process.

Nortel Ethernet Routing Switch 5500 Series

"5500 Series Switch Platforms" (page 9)outlines the switches that are part

of the 5500 Series of Nortel Ethernet Routing Switches

5500 Series Switch Platforms

5500 Series Switch Model

Nortel Ethernet Routing Switch 5510-24T

Nortel Ethernet Routing Switch 5510-48T

Nortel Ethernet Routing Switch 5520-24T-PWR

Nortel Ethernet Routing Switch 5520-48T-PWR

Nortel Ethernet Routing Switch 5530-24TFD

Key Features

A 24 port, 10/100/1GBase-T, Layer 4, diffserv-capable, stackable Ethernet switch. This switch contains two shared SFP ports.

A 48 port, 10/100/1GBase-T, Layer 4, diffserv-capable, stackable Ethernet switch. This switch contains two shared SFP ports.

A 24 port, 10/100/1GBase-T, Layer 4, diffserv-capable, stackable Ethernet switch with full Power over Ethernet (PoE) capability on all copper ports. This switch contains four shared SFP ports.

A 48 port, 10/100/1GBase-T, Layer 4, diffserv-capable, stackable Ethernet switch with full Power over Ethernet (PoE) capability on all copper ports. This switch contains four shared SFP ports.

A 24 port, 10/100/1GBase-T, Layer 4, diffserv-capable, stackable Ethernet switch. This switch contains twelve shared SFP ports and two XFP ports.

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10 Preface

Related publications

For more information about the management, conﬁguration, and use of the Nortel Ethernet Routing Switch 5500 Series, refer to the publications listed in"Nortel Ethernet Routing Switch 5500 Series Documentation" (page 10).

Nortel Ethernet Routing Switch 5500 Series Documentation

Title Description Part Number

Nortel Ethernet Routing Switch 5500 Series Release 5.1 Installation

Nortel Ethernet Routing Switch 5500 Release 5.1 Series Conﬁguration-System

Nortel Ethernet Routing Switch 5500 Release 5.1 Series Conﬁguration Security

Nortel Ethernet Routing Switch 5500 Series Release 5.1 Conﬁguration-VLANs, Spanning Tree, and Link Aggregation

Nortel Ethernet Routing Switch 5500 Release 5.1 Conﬁguration - IP Routing Protocols

Instructions for the installation of a switch in the Nortel Ethernet Routing Switch 5500 Series. It also provides an overview of hardware key to the installation, conﬁguration, and maintenance of the switch.

Instructions for the general conﬁguration of switches in the 5500 Series that are not covered by the other documentation.

Instructions for the conﬁguration and management of security for switches in the 5500 Series.

Instructions for the conﬁguration of spanning and trunking protocols on 5500 Series switches

Instructions for the conﬁguration of IP routing protocols on 5500 Series switches.

NN47200-300

NN47200-500

NN47200-501

NN47200-502

NN47200-503

Nortel Ethernet Routing Switch 5500 Series Release 5.1 Conﬁguration - Quality of Service

Nortel Ethernet Routing Switch 5500 Release 5.1 Conﬁguration- System Monitoring

Instructions for the conﬁguration and implementation of QoS and ﬁltering on 5500 Series switches.

Instructions for the conﬁguration, implementation, and use of system monitoring on 5500 Series switches.

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NN47200-504

NN47200-505

Finding the latest updates on the Nortel web site 11

Title Description Part Number

Nortel Ethernet Routing Switch 5500 Series Release Notes

- Release 5.1

Installing the Nortel Ethernet Redundant Power Supply 15

DC-DC Converter Module for the Baystack 5000 Series Switch

Nortel Ethernet Routing Switch 5500 Series Release 5.1 Installation - SFP

Provides an overview of new features, ﬁxes, and limitations of the 5500 Series switches. Also included are any supplementary documentation and document errata.

Instructions for the installation and use of the Nortel Ethernet RPS 15.

Instructions for the installation and use of the DC-DC power converter.

Instructions for the installation and use of SFP transceivers.

NN47200-400

217070-A

215081-A

NN47200-302

You can access technical documentation online at the Nortel Technical Support web site, located at http://www.nortel.com/support. Use the followingprocedure to access documents on the Technical Support web site:

•

If it is not already selected, click the Browse product support tab.

•

From the list provided in the product family box, select Nortel Ethernet Routing Switch.

• From the product list, select the desired 5500 Series Switch.

•

From the content list, select Documentation.

•

Click Go.

You can view documents online, download them for future reference, or printed them. All documents available on the Technical Support web site are in Adobe Portable Document Format (PDF) format.

Finding the latest updates on the Nortel web site

The content of this documentation was current at the time of release. To check for updates to the documentation and software for the Nortel Ethernet Routing Switch 5500 Series, use the links provided in the following table.

Software Nortel Ethernet Routing Switch 5500 Series Software Documentation "Nortel Ethernet Routing Switch 5500 Series

Documentation" (page 10)

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12 Preface

How to get help

If a service contract for the Nortel product has been purchased from a distributor or authorized reseller, contact the technical support staff for that distributor or reseller for assistance.

If a Nortel service program was purchased, contact Nortel Technical Support.

The following information is available online:

•

An ERC is available for many Nortel products and services. When an ERC is used, the call is routed to technical support personnel who specialize in supporting the service or product. The ERC for a particular product or service is available online.

The main Nortel support portal is availableat http://www.nortel.com/support.

contact information for Nortel Technical Support information about the Nortel Technical Solutions Centers information about the Express Routing Code (ERC) for your product

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An Introduction to IP Routing Protocols

This chapter provides an introduction to IP routing and IP routing protocols used in the Nortel Ethernet Routing Switch 5500 Series. Subsequent chapters will provide a more detailed description of switch capabilities and conﬁguration procedures.

IP routing

To conﬁgure IP routing on the Nortel Ethernet Routing Switch 5500 Series, use virtual local area networks (VLAN) to create virtual router interfaces by assigning an IP address to the VLAN. This section discusses this concept in depth.

For a more detailed description about VLANs and their use, consult Nortel

Ethernet Routing Switch 5500 Series Release 5.1 Conﬁguration - VLANs, Spanning Tree, and Link Aggregation.

IP addressing

An IP version 4 (IPv4) address consists of 32 bits expressed in a dotted-decimal format (XXX.XXX.XXX.XXX). The IPv4 address space is divided into classes, with classes A, B, and C reserved for unicast addresses and accounting for 87.5 percent of the 32-bit IP address space. Class D is reserved for multicast addressing. " IP address classiﬁcations" (page

13)lists the breakdown of the IP address space by address range and mask.

IP address classiﬁcations

Class

Note: Although technically part of Class A addressing, network 127 is reserved for loopback.

Address Range Mask

1.0.0.0 - 127.0.0.0 255.0.0.0 127 16,777,214

128.0.0.0 -

191.255.0.0

192.0.0.0 -

223.255.255.0

255.255.0.0 16,384 65,534

255.255.255.0 2,097,152 255

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Number of Networks

Nodes per Network

14 An Introduction to IP Routing Protocols

Class

Note: Class D addresses are primarily reserved for multicast operations although the addresses 224.0.0.5 and 224.0.0.6 are used by OSPF and 224.0.0.9 is used by RIP.

Note: Class E addresses are reserved for research purposes.

Address Range Mask

224.0.0.0 -

239.255.255.254

240.0.0.0 -

240.255.255.255

Number of Networks

Nodes per Network

To express an IP address in dotted-decimal notation, each octet of the IP address is converted to a decimal number and separated by decimal points. For example, the 32-bit IP address 10000000 00100000 00001010 10100111 is expressed in dotted-decimal notation as 128.32.10.167.

Each IP address class, when expressed in binary notation, has a different boundary point between the network and host portions of the address, as illustrated in "Network and host boundaries in IP address classes" (page

14). The network portion is a network number ﬁeld from 8 through 24 bits.

The remaining 8 through 24 bits identify a speciﬁc host on the network.

Network and host boundaries in IP address classes

Subnet addressing

Subnetworks (or subnets) are an extension of the IP addressing scheme. Subnets allow an organization to use one IP address range for multiple networks. Subnets are two or more physical networks that share a common network-identiﬁcation ﬁeld (the network portion of the 32-bit IP address).

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IP routing 15

A subnet address is created by increasing the network portion to include a subnet address, thus decreasing the host portion of the IP address. For example, in the address 128.32.10.0, the network portion is 128.32, while the subnet is found in the ﬁrst octet of the host portion (10). A subnet mask is applied to the IP address and identiﬁes the network and host portions of the address.

" Subnet masks for Class B and Class C IP addresses" (page 15)illustrates

how subnet masks used with Class B and Class C addresses can create differing numbers of subnets and hosts. This example shows the use of the zero subnet, which is permitted on a Nortel Ethernet Routing Switch 5510.

Subnet masks for Class B and Class C IP addresses

Number of bits

Subnet Mask

Number of Subnets (Recommended)

Number of Hosts per Subnet

Class B 2 255.255.192.0 2 16 382 3 255.255.224.0 6 8 190 4 255.255.240.0 14 4 094 5

255.255.248.0 30 2 046 6 255.255.252.0 62 1 022 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 1 255.255.255.128 0 126 2 255.255.255.192 2 62 3 255.255.255.224 6 30 4 255.255.255.240 14 14 5 6 255.255.255.252 62 2

255.255.255.248 30 6

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16 An Introduction to IP Routing Protocols

Variable-length subnet masking (VLSM) is the ability to divide an intranet into pieces that match network requirements. Routing is based on the longest subnet mask or network that matches.

IP routing using VLANs

The Nortel Ethernet Routing Switch 5500 Series supports wire-speed IP routing between virtual LANs (VLAN). This type of routing is also referred to as virtual routing. When a virtual router interface is created for a speciﬁed VLAN, a speciﬁc IP address is associated with the speciﬁc VLAN. In this release, the Nortel Ethernet Routing Switch 5500 Series supports static routing, in which the identiﬁers of the devices being routed between are entered manually.

This virtual router interface does not have an association with any speciﬁed port or set of ports (it is called a virtual router interface because it is not associated with any particular port). The VLAN IP address can be reached through any of the ports in the VLAN speciﬁed as a virtual router interface, and the assigned IP address is the gateway through which packets are routed out of that VLAN. Routed trafﬁc can be forwarded to another VLAN within the switch or stack of Nortel Ethernet Routing Switch 5500 Series.

Once routing is enabled on two VLANs by assigning IP addresses, routing can be performed between those two VLANs (refer to "IP routing with

VLANs" (page 16)).

IP routing with VLANs

IP routing is enabled or disabled globally on the Nortel Ethernet Routing Switch 5500 Series. By default, IP routing is disabled.

Note: All IP routing parameters can be conﬁgured on the Nortel Ethernet Routing Switch 5500 Series before routing is actually enabled on the switch.

There is no longer a one-to-one correspondence between the physical port and the router interface, because a given port can belong to multiple VLANs. The VLANs may be conﬁgured for routing on the switch.

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IP routing 17

As with any IP address, virtual router interface addresses are also used for device management. For management over IP, any virtual router interface IP address can be used to access the switch as long as routing is enabled. When the Nortel Ethernet Routing Switch 5500 Series switch or stack is used without routing enabled, the Management VLAN is reachable only through the switch or stack IP address. With IP routing enabled on the switch or stack, any of the virtual router IP interfaces can be used for management over IP.

Once routing is enabled on the Nortel Ethernet Routing Switch 5500 Series switches, the Management VLAN behaves like all other routable VLANs. The IP address is reachable through any virtual router interface, as long as a route is available. Actually, all virtual router interfaces can be used as the Management VLAN over IP.

Multinetting

The Nortel Ethernet Routing Switch 5500 Series supports the deﬁnition and conﬁguration of up to eight secondary interfaces on each VLAN (multinetting). With IP multinetting, you can associate multiple IP subnets with one VLAN. That is, connected hosts can belong to different IP subnets on the same VLAN.

Multinetting can be conﬁgured using the CLI or the Device Manager. The following diagram illustrates a network with conﬁgured IP multinetting.

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18 An Introduction to IP Routing Protocols

Network with Multinetting

You can conﬁgure a static route with the next hop on the secondary interface. You can also add static ARP for a given IP address in the same subnet of a secondary interface.

Here are some limitations when you are working with secondary interfaces:

•

you can have a maximum of eight secondary interfaces on each VLAN

•

you can have a total maximum of 256 IP interfaces (including primary and secondary)

•

all of the secondary interfaces on a VLAN are enabled or disabled together. There is no provision for conﬁguring the administrative state of the secondary IP interfaces individually.

•

dynamic routing is not available for secondary IP interfaces

• secondary interfaces are not supported on brouters

•

a primary IP interface must be in place before secondary IP interfaces can be added; secondary interfaces must be deleted before you can delete the primary

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IP routing 19

If secondary interfaces are conﬁgured on the management VLAN, routing cannot be disabled globally or on the management VLAN. Secondary IP interfaces on the management VLAN are purged from NVRAM when

•

a unit leaves the stack and the switch does not have a manually conﬁgured IP

•

the switch fails to get the IP address through the BootP mode

The following are not supported on secondary interfaces:

•

DHCRP

•

Proxy ARP

•

UDP broadcast

•

IPFIX

•

VRRP, OSPF, RIP

For information about conﬁguring secondary interfaces on VLANs, see "IP

routing using VLANs" (page 16).

Brouter port

The Nortel Ethernet Routing Switch 5500 Series supports the concept of brouter ports. A brouter port is a single-port VLAN that can route IP packets as well as bridge all non-routable trafﬁc. The difference between a brouter port and a standard IP protocol-based VLAN conﬁgured to do routing is that the routing interface of the brouter port is not subject to the spanning tree state of the port. A brouter port can be in the blocking state for non-routable trafﬁc and still be able to route IP trafﬁc. This feature removes any interruptions caused by Spanning Tree Protocol recalculations in routed trafﬁc. A brouter port is actually a one-port VLAN; therefore, each brouter port decreases the number of available VLANs by one and uses one VLAN ID.

When a brouter port is created, the following actions are also taking place on the switch:

•

A port-based VLAN is created.

•

The brouter port is added to the new port-based VLAN.

•

The PVID of the brouter port is changed to the VLAN ID of the new VLAN.

•

The STP participation of the brouter port is disabled.

•

An IP address is assigned to the brouter VLAN.

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20 An Introduction to IP Routing Protocols

Management VLAN

Prior to Software Release 4.0, the Management VLAN was the only VLAN that was used to carry the management trafﬁc, including Telnet, Web, SNMP, BootP and TFTP for the switch. The Management VLAN always exists on the switch and cannot be removed. All IP settings, including switch IP address, stack IP address, subnet mask and default gateway, apply only to the Management VLAN.

In this release of Nortel Ethernet Routing Switch 5500 Series, a regular Layer 2 (L2) VLAN behaves like a routable L3 VLAN if a pair of IP addresses and a MAC address are attached to the VLAN. When routing is enabled in L3 mode, every L3 VLAN is capable of doing routing as well as carrying the management trafﬁc. Any L3 VLAN can be used instead of the Management VLAN to manage the switch.

Layer 2 versus Layer 3 mode

When the Nortel Ethernet Routing Switch 5500 Series is conﬁgured to route IP trafﬁc between different VLANs, the switch is considered to be running in L3 mode; otherwise, the switch runs in L2 mode.

The L3 manager determines in which mode a switch or a stack should be run. The mode is determined based on the user settings and events. But the general rule is to select:

•

L3 mode: if routing is turned on globally for the switch or stack.

•

L2 mode: if routing is turned off globally for the switch or stack.

Routing and management

In L3 mode, the Management VLAN, as well as all other L3 VLANs, has the capability to route and carry the management trafﬁc. In this release of the Nortel Ethernet Routing Switch 5500 Series, the settings apply to all L3 VLANs or only to the Management VLAN. "VLAN settings" (page 20)shows all possible settings and default settings for each type of VLAN.

VLAN settings

VLAN/Feature

Management VLAN (L2 mode)

Management VLAN (L3 mode)

L3 VLAN On/off (on) On/off (on) Yes (global)

Setting IP routing

To set IP routing (or L3 VLANs), take the following steps:

Routing (default)

Off On Yes (Management

On/off (on) On No

Management (Routing)

Default Route

VLAN only)

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Step Action

IP routing 21

1 2 3

Enable IP routing globally. Assign an IP address to the speciﬁc VLAN or brouter port. Enable IP routing on the interface.

Refer to subsequent chapters in this document for detailed instructions on conﬁguring IP routes.

Address Resolution Protocol (ARP)

Network stations using the IP protocol need both a physical address and an IP address to transmit a packet. If a network station knows only a network host’s IP address, the Address Resolution Protocol (ARP) enables the network station to determine a network host’s physical address and bind the 32-bit IP address to a 48-bit MAC address. A network station can use ARP across a single network only, and the network hardware must support physical broadcasts.

If a network station wants to send a packet to a host but knows only the host’s IP address, the network station uses ARP to determine the host’s physical address as follows:

—End—

1. The network station broadcasts a special packet, called an ARP request, that asks thehost at the speciﬁed IP address to respond with its physical address.

2. All network hosts receive the broadcast message.

3. Only the speciﬁed host responds with its hardware address.

4. The network station then maps the host’s IP address to its physical address and saves the results in an address resolution table for future use.

5. The network station’s ARP table displays the association of the known MAC addresses to IP addresses.

Note: The default timeout value for ARP entries is 6 hours.

Static ARP entries can be created and individual ARP entries deleted.

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Proxy Address Resolution Protocol (Proxy ARP)

Proxy ARP allows a network station to respond to an ARP request from a locally attached host or end station for a remote destination. It does so by sending an ARP response back to the local host with its own MAC address of the network station interface for the subnet on which the ARP request was received. The reply is generated only if the switch has an active route to the destination network.

The ﬁgure below is an example of proxy ARP operation. In this example, host C with a 24-bit mask appears to be locally attached to host B with a 16-bit mask, so host B sends an ARP request for host C. However, the 5500 Series switch is between the two hosts. To enable communication between the two hosts, the 5500 Series switch would respond to the ARP request with host C’s IP address but with its own MAC address.

Proxy ARP Operation

Static routes

Once routable VLANs are created though IP address assignment, static routes can be created. Static routes allow for the manual creation of speciﬁc routes to a destination IP address. Static routes can also be used to specify a route to all networks for which there are no explicit routes in the Forwarding Information Base or the routing table. This static default route is a route to the network address 0.0.0.0 as deﬁned by the IEEE RFC 1812 standard.

Because of their static nature, this type of solution is not scalable. Thus, in a large or growing network this type of route management may not be desirable. Also, static routes do not have the capacity to determine the failure of paths. Thus, a router can still attempt to use a path after it has failed.

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Non-local static routes

The Nortel Ethernet Routing Switch 5500 Series supports the usage of non-local static routes. A non-local static route is almost identical to a static route with the exception that the next hop of the route is not directly connected to the network entity. Non-local static routes are useful in situations where there are multiple paths to a network and the number of static routes could be reduced by using only one route with a remote gateway.

Because of their static nature, this type of solution is not scalable. Thus, in a large or growing network this type of route management may not be desirable. Also, non-local static routes do not have the capacity to determine the failure of paths. Thus, a router can still attempt to use a path after it has failed.

Routing Information Protocol (RIP)

Routing Information Protocol (RIP) is a standard, dynamic routing protocol based on the Bellman-Ford (or distance vector) algorithm. It is used as an Interior Gateway Protocol (IGP). RIP allows routers to exchange information to compute routes through an IPv4-based network. The hop count, or distance, is used as a metric to determine the best path to a remote network or host. The hop count cannot exceed 15 hops (assuming a cost of one hop for each network).

IP routing 23

RIP is deﬁned in RFC 1058 for RIP version 1 and RFC 2453 for RIP version

2. The most signiﬁcant difference between the two versions is that RIP

version 2 supports subnet masks and next hop information in the RIP packet.

RIP operation

RIP uses User Datagram Protocol (UDP) data packets to exchange routing information. Each router maintains a routing table, which lists the optimal route to every destination in the system. Each router advertises its routing information by sending a routing information update at regular intervals. Neighboring routers use this information to recalculate their routing tables and retransmit the routing information. For RIP version 1, no mask information is exchanged; the natural mask is always applied by the router receiving the update. For RIP version 2, mask information is always included.

The sequence of processes governed by the routing algorithm is as follows:

1. When a router starts, it initializes the RIP data structures and then waits for indications from lower-level protocols that its interfaces are functional.

2. RIP advertisements are send on all the interfaces that are conﬁgured to send routing information.

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24 An Introduction to IP Routing Protocols

3. The neighbors will send their routing tables and the new router will update its routing table based on the advertisements received.

4. From now on periodic updates are send by each router in the network to ensure a correct routing database.

If a router does not receive an update from another router within a timeout period, it deletes the routes served by the nonupdating router from its routing table. However, it keeps these routes temporarily in a garbage list and continues to advertise them with a metric of 16 for a holddown period, so that neighbors know that the routes are unreachable. If a valid update for a garbage route is received within the holddown period, the router adds the route back into its routing table. If no update is received, the router completely deletes all garbage list entries for the nonupdating router.

To prevent routing loops and to promote fast convergence, RIP uses the mechanisms of split horizon, with or without poisoned reverse, and triggered updates. Simple split horizon means that IP routes learned from a neighbor are not advertised back in updates to that neighbor. Split horizon with poisoned reverse means that these routes are advertised back to the neighbor, but they are “poisoned” with a metric of 16, which represents inﬁnite hops in the network. The receiver neighbor therefore ignores this route. Triggered updates means that a router is required to send update messages whenever it changes the metric for a route, even if it is not yet time for a regular update message.

RIP sends routing information updates every 30 seconds. These updates contain information about known networks and the distances (hop count) associated with each. For RIP version 1, no mask information is exchanged; the natural mask is always applied by the router receiving the update. Mask information is always included for RIP version 2.

If information about a network is not received for within the allotted timeout period (180 seconds by default), it is removed from the routing table and the route is moved to the garbage list . From the garbage list it will be advertised for the allotted holdown period (120 seconds by default) with metric set to inﬁnity (16). These timers can be changed by conﬁguring the RIP Interface Timeout Timer and Holddown Timer parameters.

RIP supports the following standard behavior:

•

periodic RIP updates about effective best routes

•

garbage collection

•

split horizon with or without poisoned reverse

•

triggered update for changed RIP routes

•

unicast to the speciﬁc query requestor

•

broadcast/multicast of regular and triggered updates

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•

subnet mask (RIP version 2)

•

routing table update based on the received RIP message

•

global update timer

•

holddown timer and timeout timer per device and per interface

•

cost per device and per interface

The Nortel Ethernet Routing Switch 5500 Series implementation of RIP also supports the following features:

•

in and out routing policies

•

auto-aggregation (also known as auto-summarization) of groups of adjacent routes into single entries

Many RIP features are conﬁgurable. The actual behavior of the protocol depends on the feature conﬁgurations.

RIP metrics

RIP is known as a distance vector protocol. The vector is the network number and next hop, and the distance is the cost associated with the network number. RIP identiﬁes network reachability based on cost, and cost is deﬁned as hop count. The distance from one router to the next is considered to be one hop. This cost or hop count is known as the metric The illustration below depicts the hop counts between various units in a network.

RIP hop counts

A directly connected network has a metric of zero. An unreachable network has a metric of 16. Therefore, 15 hops or 15 routers is the highest possible metric between any two networks.

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RIP Send and Receive Modes

RIP can be conﬁgured to use a number of different send and receive modes depending on the speciﬁcs of the network conﬁguration. The following table lists the send and receive modes supported.

RIP send and receive modes

Send Mode

Description Result

rip1comp This mode is used to

broadcast RIP version 2 updates using RFC 1058 route consumption rules. This is the default send mode for the Nortel Ethernet Routing Switch 5500 Series.

rip1 This mode is used to

broadcast RIP updates that are compliant with RFC 1058.

•

Destination MAC is a broadcast, ff-ff-ff-ff-ff-ff

•

Destination IP is a broadcast for the network (for example,

192.1.2.255)

•

RIP Update is formed as a RIP version 2 update, including network mask

•

RIP version = 2

• Destination MAC is a broadcast, ff-ff-ff-ff-ff-ff

• Destination IP is a broadcast for the network (for example,

192.1.2.255)

•

RIP Update is formed as a RIP version 1 update, no network mask included

• RIP version = 1

rip2 This mode is used to

nosend No RIP updates are sent

Receive Mode

•

Destination MAC is a multicast,

broadcast multicast RIP version 2 updates.

01-00-5e-00-00-09

•

Destination IP is the RIP version 2 multicast address, 224.0.0.9

•

RIP Update is formed as a RIP version 2 update including network mask

•

RIP version = 2

None

on the interface.

Result

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rip1OrRip2 RIP version 1 or RIP version 2 updates are accepted. rip1 RIP version 1 and RIP version 1 compatible updates only are

accepted.

rip2 RIP version 2 updates only are accepted.

Limitations

RIP has the following limitations:

•

The protocol is limited to networks whose longest path is 15 hops.

•

The protocol depends on counting to inﬁnity to resolve certain unusual situations.

•

The protocol uses ﬁxed metrics (the hop number)to compare alternative routes, as opposed to real-time parameters such as measured delay, reliability, or load.

•

RIP does not support address-less links.

Open Shortest Path First (OSPF) protocol

The Open Shortest Path First (OSPF) Protocol is an Interior Gateway Protocol (IGP) that distributes routing information between routers belonging to a single autonomous system (AS). Intended for use in large networks, OSPF is a link-state protocol which supports IP subnetting and the tagging of externally-derived routing information.

IP routing 27

Note: The Nortel Ethernet Routing Switch 5500 Series implementation of OSPF only supports broadcast and passive interfaces. Point-to-point and NBMA interfaces are not supported.

Overview

In an OSPF network, each router maintains a link-state database that describes the topology of the autonomous system (AS). The database contains the local state for each router in the AS, including the router’s usable interfaces and reachable neighbors.

Each router periodically checks for changes in its local state and shares any changes detected by ﬂooding link-state advertisements (LSAs) throughout the AS. Routers synchronize their topological databases based on the sharing of information from LSAs.

From the topological database, each router constructs a shortest-path tree, with itself as the root. The shortest-path tree gives the optimal route to each destination in the AS. Routing information from outside the AS appears on the tree as leaves.

OSPF routes IP trafﬁc based solely on the destination IP address and subnet mask contained in the IP packet header.

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Beneﬁts

Beneﬁts in large networks OSPF offers the following beneﬁts:

•

Fast convergence In the event of topological changes, OSPF recalculates routes quickly.

•

Minimal routing protocol trafﬁc Unlike distance vector routing protocols such as RIP, OSPF generates a

minimum of routing protocol trafﬁc.

•

Load sharing OSPF provides support for equal-cost multipath routing. If several

equal-cost routes to a destination exist, trafﬁc is distributed equally among them.

•

Because OSPF does not use hop count in its calculation, the routing domain is scalable.

OSPF routing algorithm

A separate copy of the OSPF routing algorithm runs in each area. Routers which are connected to multiple areas run multiple copies of the algorithm. The sequence of processes governed by the routing algorithm is as follows:

1. When a router starts, it initializes the OSPF data structures and then waits for indications from lower-level protocols that its interfaces are functional.

2. A router then uses the Hello Protocol to discover neighbors. On point-to-point and broadcast networks the router dynamically detects its neighbors by sending hello packets to the multicast address AllSPFRouters. On non-broadcast multiaccess networks, some conﬁguration information is required in order to discover neighbors.

3. On all multiaccess networks (broadcast or non-broadcast), the Hello Protocol also elects a DR for the network.

4. The router attempts to form adjacencies with some of its neighbors. On multiaccess networks, the DR determines which routers become adjacent. This behavior does not occur if a router is conﬁgured as a passive interface, because passive interfaces do not form adjacencies.

5. Adjacent neighbors synchronize their topological databases.

6. The router periodically advertises its link-state, and also does so when its local state changes. LSAs include information about adjacencies enabling quick detection of dead routers on the network.

7. LSAs are ﬂooded throughout the area, ensuring that all routers in an area have exactly the same topological database.

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8. From this database each router calculates a shortest-path tree, with itself as root. This shortest-path tree in turn yields a routing table for the protocol.

OSPF router types

Routers in an OSPF network can take on different roles depending their conﬁguration. The following table describes the router types in an OSPF network.

OSPF router types

Router Type Description

Autonomous System Boundary Router (ASBR)

Area Border Router (ABR)

Internal Router (IR) A router that has interfaces only within a single area

Designated Router (DR)

Backup Designated Router (BDR)

A router attached at the edge of an OSPF network is called an AS boundary router (ASBR). An ASBR generally has one or more interfaces that run an inter-domain routing protocol. In addition, any router distributing static routes or RIP routes into OSPF is considered an ASBR. The ASBR forwards external routes into the OSPF domain. In this way, routers inside the OSPF network learn about destinations outside their domain.

A router attached to two or more areas inside an OSPF network is considered an area border router (ABR). ABRs play an important role in OSPF networks by condensing the amount of OSPF information that is disseminated.

inside an OSPF network is considered an internal router (IR). Unlike ABRs, IRs have topological information only about the area in which they are contained.

In a broadcast network a single router is elected to be the designated router (DR) for that network. A DR assumes the responsibility of making sure all routers on the network are synchronized with one another and also advertises that network to the rest of the AS.

A backup designated router (BDR) is elected in addition to the designated router (DR) and, in the event of failure of the DR, will assume its role quickly.

OSPF host route

An OSPF router with hosts directly attached to its interfaces can use host routes to advertise the attached hosts to its neighbors. You can conﬁgure up to 32 host routes.

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Host routes are managed with Nortel Networks Command Line Interface (NNCLI) commands and SNMP MIBs and are identiﬁed by the host IP address and the conﬁgured route type of service (TOS). For each host directly connected to the router, conﬁgure the cost of the link to the host during host creation. You cannot modify this cost.

Note: Always set TOS to 0 because TOS-based routing is not supported.

When a host is added to, or deleted from, a host route, the router updates the router LSAs and ﬂoods them to neighbors in each area where that router has an interface.

Followingis an exampleof parameters fora host route advertised in the LSA.

Host route in LSA

•

Type: 3 (stub network)

•

LinkID: IP address of host directly connected to router

•

Link Data: 0xFFFFFFFF

•

Metric: conﬁgured cost of host

OSPF Enhancements

•

Host route - Allows a router to advertise to its neighbors all hosts that are directly attached to that router’s interfaces. Up to 32 host routes can be conﬁgured.

•

Virtual links - The OSPF network can be partitioned into multiple areas. However, a backbone area must exist and be contiguous, and every non-backbone area must be connected to the backbone area using either a physical or a logical link. In a network where a physical connection between the non-backbone area and backbone area is impossible, use of a virtual link provides the logical connection through another non-backbone area, called the transit area. Virtual links can be created manually or automatically. The 5500 Series switch supports up to 16 virtual links.

When 5500 Series switches are stacked, and a unit leaves the stack and becomes standalone, the router ID is automatically changed to its default value if IP blocking is turned off and OSPF is globally enabled. This prevents duplication of a router ID in the OSPF routing domain. The new router ID value is temporary, that is, it is not saved to NVRAM. Therefore, upon reset, the old router ID is restored. Conﬁgurable using NNCLI, ACG, and Device Manager.

Example conﬁgurations The following is an example for creating a host route:

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