Cabletron Systems NB20E User manual

NB20E and NB25 E

TWO PORT ETHERNET BRIDGES

USER’S MANUAL

CABLETRON SYSTEMS, P.O. BOX 6257, ROCHESTER, NH 03867-6257

NOTICE

Cabletron Systems reserves the right to make changes in speciﬁcations

and other information contained in this document without prior notice.

The reader should in all cases consult Cabletron Systems to determine

whether any such changes have been made.

The hardware, ﬁrmware, or software described in this manual is subject to

change without notice.

IN NO EVENT SHALL CABLETRON SYSTEMS BE LIABLE FOR

ANY INCIDENTAL, INDIRECT, SPECIAL, OR CONSEQUENTIAL

DAMAGES WHATSOEVER (INCLUDING BUT NOT LIMITED TO

LOST PROFITS) ARISING OUT OF OR RELATED TO THIS

MANUAL OR THE INFORMATION CONTAINED IN IT, EVEN IF

CABLETRON SYSTEMS HAS BEEN ADVISED OF, KNOWN, OR

SHOULD HAVE KNOWN, THE POSSIBILITY OF SUCH DAMAGES.

Cabletron Systems Inc.

P.O. Box 6257, E. Rochester, NH 03867-6257

Printed in the United States of America

Order Number: 9030040-02 May 90

Remote

LANVIEW

NB25E

NB20E

, and

LAN-MD

are

trademarks of Cabletron Systems Inc.

FCC NOTICE

This device complies with Part 15 of the FCC rules. Operation is subject

to the following two conditions: (1) this device may not cause harmful

interference, and (2) this device must accept any interference received,

including interference that may cause undesired operation.

WARNING:

This equipment uses and generates and can radiate radio

frequency energy and if not installed properly and used in accordance

with the instruction manual, may cause interference to radio

communications. It has been tested and found to comply with the limits

for a Class A digital device pursuant to Subpart J, of Part 15, of the FCC

rules., which are designed to provide reasonable protection against such

interference in a commercial environment. Operation of this equipment in

a residential area is likely to cause interference in which case the user at

his own expense will be required to correct the interference.

If this equipment does cause interference to radio or television, which can

be determined by turning the equipment off and on, the user is

encouraged to try to correct the interference by one or more of the

following measure:

• Re-orient the receiving antenna.

• Relocate the antenna with respect to the bridge.

• Move the bridge away from the receiver.

• Plug the bridge into a different outlet so that the bridge and the

receiver are on different branch circuits.

If necessary, the user should consult the dealer or an experienced radio/

television technician for additional suggestions. The user may ﬁnd the

following booklet prepared by the Federal Communication Commission

helpful:

“How to Identify and Resolve Radio TV Interference Problems”

This booklet is available from the U.S. Government Printing Ofﬁce,

Washington, D.C. 20401- Stock No. 004-000-00345-4

iii

CONTENTS

CHAPTER 1 INTRODUCTION

1.1 USING THIS MANUAL................................................................1-1

1.2 GETTING HELP..........................................................................1-2

1.3 THE NB20E AND NB25E TWO PORT ETHERNET BRIDGE ....1-2

1.4 THE BRIDGE FILTERING METHOD..........................................1-3

1.5 MULTIPLE BRIDGE ENVIRONMENTS......................................1-5

1.5.1 The Root Bridge..............................................................1-5

1.5.2 Primary and Redundant Data Paths...............................1-6

1.6 REMOTE LANVIEW....................................................................1-7

1.7 RELATED MANUALS..................................................................1-8

CHAPTER 2 INSTALLATION REQUIREMENTS/

SPECIFICATIONS

2.1 LOCATION REQUIREMENTS....................................................2-1

2.2 NETWORK REQUIREMENTS....................................................2-1

2.3 OPERATING SPECIFICATIONS ................................................2-2

CHAPTER 3 INSTALLINGTHE NB20E OR NB25E BRIDGE

3.1 UNPACKING THE NB20E OR NB25E BRIDGE.........................3-1

3.2 INSTALLING THE BRIDGE.........................................................3-1

3.2.1 Installing the Rack Mount Brackets ................................3-2

3.2.2 Cable Support Installation...............................................3-3

3.2.3 Connecting The Bridge To The Network ........................3-3

3.2.4 Setting The Mode Switches............................................3-4

3.2.5 Connecting The NB20E or NB25E To

The Power Source.........................................................3-5

CHAPTER 4 TESTING AND LANVIEW

4.1 INSTALLATION CHECK-OUT.....................................................4-1

4.2 USING LANVIEW........................................................................4-2

4.3 USING THE FORWARD BROADCAST SWITCH.......................4-3

4.4 USING THE ROOT SWITCH ......................................................4-4

CONTENTS

1-1

CHAPTER 1

INTRODUCTION

Welcome to the Cabletron Systems NB20E™ and NB25E™ Two Port

Ethernet Bridges User's Manual. We have designed this user’s manual to

serve as a simple installation and reference guide for the NB20E and

NB25E, and to explain the capabilities and special features of each

individual bridge. With the appropriate design, the Cabletron Systems

NB25E or NB20E can dramatically improve network performance and

bandwidth efﬁciency on heavily utilized network segments.

You should read through this manual to gain a full understanding of the

NB20E and NB25E Bridges and their capabilities.

1.1 USINGTHIS MANUAL

Chapter 1,

Introduction

, discusses the capabilities of Cabletron Systems'

NB20E or NB25E Two Port Ethernet Bridge. An explanation of the

bridge ﬁltering process and a discussion of bridge functionality in

multi-bridge environments are also included. The chapter concludes with

a list of related manuals.

Chapter 2,

Installation Requirements/Speciﬁcations

, contains a list of

hardware, software, location and environmental requirements that must be

met before you install either bridge.

Chapter 3,

Installing the NB20E or NB25E Bridge

, contains

instructions for installing the NB20E or the NB25E Two Port Ethernet

Bridge.

Chapter 4,

Testing and Troubleshooting

, provides procedures for testing

and troubleshooting the installation of the NB20E or the NB25E Bridge.

Instructions for using LANVIEW™, Cabletron Systems’built-in visual

diagnostic and status monitoring system, are also included.

We assume that you have a general working knowledge of Ethernet or

IEEE 802.3 type data communications networks and their physical layer

components.

INTRODUCTION

1-2

1.2 GETTING HELP

If you need additional support related to the Cabletron Systems NB20E or

NB25E Two Port Ethernet Bridge, or if you have any questions,

comments or suggestions related to this manual, feel free to contact

Cabletron Systems' Technical Support at:

Cabletron Systems Inc.

P.O. Box 6257

E. Rochester, NH 03867-6257

Phone: (603) 332-9400

1.3 THE NB20E AND NB25ETWO PORT ETHERNET

BRIDGE

With the Cabletron Systems NB20E or NB25E Two Port Ethernet Bridge,

you can dramatically increase the performance of two 10 Mbit per second

Ethernet networks efﬁciently and economically, regardless of the media

type. The bridges are designed to increase the efﬁciency of bandwidth use

across a LAN by building a list of local node addresses as it learns which

nodes are located on each side of the bridge. This list is called the Source

Address Table. The bridge uses the Source Address Table to determine

which data packets should be allowed to cross the bridge, keeping local

trafﬁc local.

The NB20E Bridge uses a software ﬁlter database to check destination

addresses against its Source Address Table. The NB25E Bridge uses a

higher performance hardware ﬁlter database. Both bridges are equipped

with a feature called Aging Time, that continually makes space for new

entries into the Source Address Table by deleting addresses that are not

frequently used.

The NB20E and NB25E are designed to function in multiple-bridge

environment. As IEEE 802.1 compliant bridging units, the bridges

incorporate a Spanning Tree Algorithm to detect potential data loops in

the network. Spanning TreeAlgorithm is a hierarchy (or tree) of priorities

that is established between bridges.

The NB20E and NB25E can be controlled and managed by Cabletron

Systems' Remote LANVIEW™ - Network Control Management for the

Cabletron Systems' NB20E and NB25E. Remote LANVIEW provides the

most complete network management system for Ethernet networks in the

industry today. With Remote LANVIEW, a bridge can be managed

INTRODUCTION

1-3

according to the speciﬁc needs of a network manager. The network

manager's ability to set up parameters within Remote LANVIEW ensures

optimal performance for each bridge, and hence, each network. For

example, a network manager can manage and monitor: the ﬂow of trafﬁc

through a bridge, the status of a database, the bridge protocol and port

parameters, and the bridge setup.

Both bridges also incorporate Cabletron Systems' LANVIEW Status

Monitoring and Diagnostics Systems. Should a problem arise,

LANVIEW's LEDs will help you to diagnose problems, such as power

failures or cable faults. Individual or separate LEDs advise you that: the

bridge is on line and operational, the bridge is receiving or transmitting

data packets, or the bridge is detecting a collision signal from an

individual segment.

The NB20E or NB25E Bridge interconnects networks consisting of

Ethernet Version 1, Version 2, and/or IEEE 802.3 equipment. The bridge

has two AUI ports so it can be connected directly to any of Cabletron’s

many Ethernet transceivers for data transmission over various media

including twisted pair, ﬁber optic, and/or thick or thin Ethernet coaxial

cable.

1.4 THE BRIDGE FILTERING METHOD

The Cabletron Systems NB20E and NB25E prevent unnecessary network

trafﬁc from passing through the bridge, by implementing a ﬁltering

process. This process begins with the creation of a list of local node

addresses in a table referred to as the Source Address Table.

When the NB20E or NB25E ﬁrst goes on line, the bridge initially

forwards all packets through the bridge.As the bridge receives a packet, it

learns the address of the sending node from the packet and stores that

address in its Source Address Table, indicating the segment on which the

address resides. In this manner, the bridge learns the address of each node

on each side of the bridge and is able to use the addresses stored in the

table to compare the destination address of each subsequent packet that

travels to the bridge. If the destination address of a packet is located on

the same segment (local segment) as the sending node, the packet is not

forwarded across the bridge.

Figure 1-1 provides an illustration of the ﬁltering process.

INTRODUCTION

1-4

Figure 1-1 Bridging Method

In this example, when NodeA sends a packet to Node B, the bridge learns

Node A’s source address and adds the address to the Source Address

Table, indicating that the node is on LAN 1. If Node C subsequently sends

a packet to Node A, Node A’s address will be detected in the Source

Address Table for LAN 1 and the packet will not be forwarded across the

bridge to LAN 2. At the same time, the bridge will learn Node C’s source

address and add it to the SourceAddress Table, indicating that the node is

on LAN 1.

If the destination address of a packet is located on a different segment, the

bridge will forward the packet across the bridge. If Node B sends a packet

to Node A, the bridge will compare the destination address of the packet

against the addresses in the SourceAddress Table. It will then detect Node

A as being on the other side of the bridge and forward the packet through

the bridge to LAN 1. The bridge will store the address of Node B to

indicate that Node B is on LAN 2.

If no packets are sent from a source address in a ﬁve minute interval, that

address will be deleted from the bridge’s Source Address Table.

NODE A NODE C

LAN 1

LAN 2

NODE B

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