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Document:	DECbridge 90 Owners Manual
Order Number:	EK-DEWGB-OM
Revision:	B01
Pages:	72
Original Filename:

OCR Text

DECbridge 90
Owner’s Manual
Order Number: EK-DEWGB-OM. B01

Revision/Update Information:

Digital Equipment Corporation
Maynard, Massachusetts

This is a revised manual.

First Edition, April 1991
Second Edition, September 1992
The information in this document is subject to change without notice and should not be construed
as a commitment by Digital Equipment Corporation. Digital Equipment Corporation assumes no
responsibility for any errors that may appear in this document.
The software described in this document is furnished under a license and may be used or copied
only in accordance with the terms of such license.
No responsibility is assumed for the use or reliability of software on equipment that is not supplied
by Digital Equipment Corporation or its affiliated companies.
Restricted Rights: Use, duplication, or disclosure by the U.S. 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.

© Digital Equipment Corporation 1991, 1992.
All Rights Reserved.
Printed in U.S.A.
FCC NOTICE: The equipment described in this manual generates, uses, and may emit radio
frequency energy. The equipment has been type tested and found to comply with the limits for
a Class A computing device pursuant to Subpart J of Part 15 of FCC Rules, which are designed
to provide reasonable protection against such radio frequency interference when operated in a
commercial environment. Operation of this equipment in a residential area may cause interference,
in which case the user at his own expense may be required to take measures to correct the
interference.
The following are trademarks of Digital Equipment Corporation: BI, DEC, DECbridge, DECconnect,
DECmcc, DECnet, DECserver, Digital, LAT, MicroVAX, ThinWire, ULTRIX, UNIBUS, VAX,
VAX–11/780, VAX–11/785, VAX 3600, VAX 3900, VAX 6000, VAX 6300, VAX 6400, VAX 9000,
VAXcluster, VAX DOCUMENT, VAXELN, VAXstation, VMS, VT, and the DIGITAL logo.

This document was prepared using VAX DOCUMENT, Version 2.0.

Contents
About This Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

vii

1 Overview
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DECbridge 90 Front Panel Lights and Switches . . . . . . . . . . . . . .

1–1
1–2
1–3

2 Configuring the DECbridge 90
Supported Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2–4

3 Installation
Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Site Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Standalone Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mount DECbridge 90 on a Wall . . . . . . . . . . . . . . . . . . . . . . . .
Make Connections for Standalone Installations . . . . . . . . . . . .
Work Group Connection . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Supply Connection . . . . . . . . . . . . . . . . . . . . . . . . . .
Backplane Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Install the DECbridge 90 in the DEChub 90 Backplane . . . . .
Make Connections for Backplane Installations . . . . . . . . . . . .

3–1
3–2
3–2
3–3
3–5
3–7
3–7
3–8
3–9
3–9

4 Managing the DECbridge 90
DECbridge 90 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DECbridge 90 Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Spanning Tree Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Spanning Tree Algorithm Properties . . . . . . . . . . . . . . . . . . . .
MOP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MOP Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4–1
4–2
4–3
4–3
4–3
4–3

iii

Accessing MOP from VMS Systems . . . . . . . . . . . . . . . . . . . . .
Accessing MOP from ULTRIX Systems . . . . . . . . . . . . . . . . . .
Console Carrier User Interface . . . . . . . . . . . . . . . . . . . . . . . .
Console Carrier Command Language . . . . . . . . . . . . . . . . . . . . . . .
Description of Command Parameters . . . . . . . . . . . . . . . . . . . .
Description of Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Protocol Filtering Examples . . . . . . . . . . . . . . . . . . . . . . . . . . .
Remote Bridge Management Software (RBMS) . . . . . . . . . . . .
Error Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4–4
4–6
4–6
4–7
4–9
4–10
4–17
4–19
4–20

5 Troubleshooting
Customer Services Option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5–5

A Specifications and Parts List
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A–3

B Related Documentation
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Continental USA and Puerto Rico . . . . . . . . . . . . . . . . . . . . . .
New Hampshire, Alaska, and Hawaii . . . . . . . . . . . . . . . . . . .
Outside the USA and Puerto Rico . . . . . . . . . . . . . . . . . . . . . .
Digital Personnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

B–1
B–1
B–2
B–2
B–2

Index
Figures
1–1
1–2
2–1
2–2
2–3
2–4
2–5
2–6
3–1
3–2

Sample DECbridge 90 Connection . . . . . . . . . . . . . . . .
Indicators and Connectors . . . . . . . . . . . . . . . . . . . . . .
DECbridge 90 Configured to ThinWire Backbone . . . .
DECbridge 90 Configured to AUI Backbone . . . . . . . . .
Work Group With More Than 200 Stations . . . . . . . . .
Redundant Connections . . . . . . . . . . . . . . . . . . . . . . . .
Bridges in Work Group . . . . . . . . . . . . . . . . . . . . . . . .
Multiple Bridges in a Work Group . . . . . . . . . . . . . . . .
Standalone Installation . . . . . . . . . . . . . . . . . . . . . . . .
Removing the Back Cover . . . . . . . . . . . . . . . . . . . . . .

1–3
1–4
2–2
2–3
2–5
2–6
2–7
2–8
3–3
3–4

3–3
3–4
3–5
3–6

Connecting Transceiver Cables . . . . . . . . . . . . . . . . . .
Connecting to the Middle of a ThinWire Segment . . . .
Connecting to the End of a ThinWire Segment . . . . . .
Installing the DECbridge 90 into DEChub 90
Backplane Slot 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3–6
3–7
3–7

Ethernet Circuit Names for Systems . . . . . . . . . . . . . .
Summary of DECbridge 90 Commands . . . . . . . . . . . .
Protocol Type Codes and Names . . . . . . . . . . . . . . . . .
DECbridge 90 Error Messages . . . . . . . . . . . . . . . . . . .
Activity Indicators (LEDs) . . . . . . . . . . . . . . . . . . . . . .
Simple Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . .
Physical Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating Environment . . . . . . . . . . . . . . . . . . . . . . . .
Shipping Environment . . . . . . . . . . . . . . . . . . . . . . . . .
Power Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . .
Standalone Installation Kit Contents . . . . . . . . . . . . . .
DEChub 90 Backplane Installation Kit Contents . . . . .

4–5
4–7
4–17
4–20
5–2
5–4
A–1
A–2
A–2
A–2
A–3
A–3

3–8

Tables
4–1
4–2
4–3
4–4
5–1
5–2
A–1
A–2
A–3
A–4
A–5
A–6

About This Manual
This manual provides an overview of the DECbridge 90 unit and describes how
to configure, install, operate, manage, and troubleshoot the DECbridge 90. This
manual also provides the specifications and lists the related documentation for
the DECbridge 90.
In this manual, the DECbridge 90 unit may be referred to as the DECbridge 90,
work group bridge, bridge, or WGB.

Organization
This manual has five chapters and two appendices.
Chapter

Description

Provides an overview of the DECbridge 90, including features,
description of front panel indicators, and configurations.

Provides configuration rules for the DECbridge 90.

Describes how to install the DECbridge 90.

Describes how to manage the DECbridge 90 through the
Maintenance Operations Protocol (MOP) or Network Control
Program (NCP).

Describes how to troubleshoot the DECbridge 90.

Appendix A

Describes the physical dimensions; the environmental,
electrical, and power specifications; and provides a parts
list.

Appendix B

Provides a list of related documentation and ordering
information.

vii

Conventions
The following conventions are used in this manual:
Convention

Meaning

Note

Provides general information.

boldface type

Boldface type in examples indicates user input. For example:

DECbridge> SET PROTOCOL
parameters

Parameters are italicized. For example:
SHOW PORT slot number

[]

Characters within brackets represent optional parameters. For
example:
SHOW PORT [hub number, slot number]

viii

1
Overview
The DECbridge 90 unit offers a reliable, high-performance, easy-to-install means
of connecting two local area networks (LANs). Configured as a standalone unit
or in the DEChub 90 backplane, the DECbridge 90 provides greater network
reliability and efficiency by allowing the local area network to be partitioned into
a number of smaller LANs.

Features
The following list summarizes the main features of the DECbridge 90:
•

Easy-to-use

•

Support of spanning tree algorithm

•

Plug-and-go installation

•

Activity LEDs for easy diagnosis

Management through Maintenance
Operations Protocol (MOP) console
carrier

•

Small size

•

Rack-mountable in DEChub 90
backplane

Support of Remote Bridge Management
Software (RBMS)

•

ThinWire and 15-pin AUI Ethernet
interfaces

•

Frame filtering and frame forwarding
at full network throughput

•

Protocol filtering

Overview 1–1

Description
The DECbridge 90 is a specialized LAN device that connects two Ethernet or
IEEE 802.3 LANs to form a single extended local area network (Figure 1–1).
One LAN, referred to as the backbone, can consist of an unrestricted number of
stations. The other LAN, referred to as the work group, is usually the smaller
of the two LANs and is optimized for LANs of fewer than 200 stations. When the
work group consists of fewer than 200 stations, the DECbridge 90 automatically
prevents unnecessary traffic from being transmitted from one LAN to the other.
When there are more than 200 stations in the work group, the DECbridge 90
enters flood mode, which reduces the effectiveness of the traffic isolation,
but ensures full connectivity across the bridge. (Refer to Chapter 4 for more
information about flood mode.)
The DECbridge 90 provides the network manager with additional control over
traffic distribution through protocol filtering and repeater management features.
All stations connected within the extended LAN communicate with one another
as if they were all on the same LAN. The connected LANs will work in networks
using equipment designed to be compatible with the Ethernet or IEEE 802.3
standards. The DECbridge 90 connects to the work group using a ThinWire
(10Base2) integral transceiver. The backbone connections are made through a
15-pin AUI Ethernet (10Base5) interface.
Figure 1–1 shows a sample DECbridge 90 connection.

1–2 Overview

Figure 1–1 Sample DECbridge 90 Connection

Workstations

Terminals

DECrepeater 90C

DECrepeater 90T

DECserver 90L

Workstation

Work Group

Personal Computer

ThinWire

Segment

DECbridge 90/90FL
Work Group Bridge
Work Group

Computer

Ethernet

Backbone

Computer

Server
LJ-02073-TI0

DECbridge 90 Front Panel Lights and Switches
The front panel of the DECbridge 90 contains several indicator lights and two
switches (Figure 1–2). The lights (LEDs) indicate the status of the DECbridge 90.
One of the switches is used to select ThinWire or AUI connection; the other
switch is used to reset the DECbridge 90 password. When you push the reset
button, any existing password is nullified and the DECbridge 90 is accessible
without a password until you define a new password. For an explanation of the
DEFINE BRIDGE PASSWORD command, refer to the Description of Commands
section in Chapter 4.

Overview 1–3

Figure 1–2 shows the DECbridge 90 indicators and connectors.
Figure 1–2 Indicators and Connectors
14

1
2
3
4
5

7
8

9
10
11
12
13

LJ-00067-TI0

DC OK Indicator - (Green) Turns on when power supply is providing
power to the bridge.
System OK Indicator - (Green) Turns on when bridge is powered up and
reset and has successfully completed self-test.

1–4 Overview

Work Group Port OK Indicator - (Green) Turns on when bridge is
powered up and reset and has successfully completed work group port
self-test. Will turn off whenever a fault is detected on the port; turns on
when the fault has been cleared.

Work Group Port Activity Indicator - (Green) Blinks when the LAN
connected to the work group port is receiving messages; does not blink
when transmitting messages.

Bridge Forwarding State - (Yellow) Turns on when bridge is not
forwarding messages. Turns on for a short period of time during power
up. Remains off during normal operation.
Maximum Work Group Size Exceeded Indicator - (Yellow) Turns on
when the recommended maximum size (200) of the work group has been
exceeded.
Backbone Port OK Indicator - (Green) Turns on when the bridge is
powered up and reset and has successfully completed backbone port selftest. Will turn off whenever a fault is detected on the port; turns on when
the fault has been cleared.

Backbone Port Activity Indicator - (Green) Blinks when there is
received activity on the LAN connected to the backbone port; does not blink
for transmitted messages.

Ethernet Address - Unique physical address of the bridge, comprised of
six 2-digit hexadecimal numbers.
Backbone Port ThinWire Connector - Provides ThinWire connection to
backbone port of the DECbridge 90.
ThinWire/AUI Selector - Selects ThinWire or AUI connection to the
backbone.

Backbone Port AUI Connector - Provides AUI connection to the
backbone port of the DECbridge 90.

Password Reset Switch - Nullifies the password for the DECbridge 90.
The bridge is accessible without a password until a new password is
defined.

Work Group Port ThinWire Connector - Provides ThinWire connection
to the work group port of the DECbridge 90.
Backplane Connector - Provides work group network connection to the
DECbridge 90 when it is installed in the DEChub backplane.
Power Connector - Provides +5.0 V and +12.0 V from the DECbridge 90
power supply (standalone) or the DEChub 90 power supply (mounted).
Cover - Covers the backplane connector and mounting assembly.

Overview 1–5

2
Configuring the DECbridge 90
The DECbridge 90 unit has several configuration rules and guidelines that must
be followed during installation and use.
Each LAN connected by the DECbridge 90 is required to be an Ethernet or
IEEE 802.3 compliant CSMA/CD LAN. The backbone port of the DECbridge 90
provides both ThinWire Ethernet (10Base2) and AUI (10Base5) connections,
as shown in Figure 2–1 and Figure 2–2. The work group port provides only a
ThinWire Ethernet (10Base2) connection.
Figure 2–1 shows the DECbridge 90 configured to a ThinWire backbone.

Configuring the DECbridge 90 2–1

Figure 2–1 DECbridge 90 Configured to ThinWire Backbone
5 0- ohm
T er minator

Ba ckb o n e
50-ohm
Te r m i n a to r

S ystem

System

Syste m

B a c k b o n e Po r t
T h i n w i re Co n n e cti o n
50-ohm
Te r m i n a to r

Work
Gr o u p
Br i d g e

5 0 -o h m
T e rm i n a t o r

System

Syste m

LJ-00247-TI0

2–2 Configuring the DECbridge 90

Figure 2–2 shows the DECbridge 90 configured to an AUI backbone.
Figure 2–2 DECbridge 90 Configured to AUI Backbone

S ystem

System

50-ohm
Te rmi n at o r

50-ohm
T e r mi n a t o r
Transceiver

H4005

Transceiver

T - Co n n e c t o r
wi t h T e r mi n a t o r
A UI
Connecto r

Work
Group
Bridge

5 0-ohm
T e rmi n at o r

S y s t em

S ystem

System

LJ-00244-TI0

Configuring the DECbridge 90 2–3

Supported Configurations
There are several reasons to configure bridges into an extended LAN:
•

To connect different media types.

•

To extend the range of the LAN. (For example, to attach a DEChub 90 to an
AUI backbone.)
Cable length and repeater configuration rules are considered separately in
each LAN.

•

To control traffic by protocol type, by separating the LAN into networks for
selected protocols. (For example, to keep VAXcluster traffic confined within a
work group.)

•

To automatically control traffic by keeping messages between stations on the
same LAN from being retransmitted on the other LAN.

The following network configurations may require special consideration:
•

Work group size
To automatically isolate traffic, the work group should consist of less than 200
stations. When the number of stations in a work group exceeds 200, the Work
Group Size Exceeded light will come on indicating that flood mode is enabled
(indicator light number 6 shown in Figure 1-2). Refer to Chapter 4 for further
information about flood mode.
To avoid enabling flood mode when a work group consists of more than
200 stations, separate the work group into smaller groups of less than 200
stations each with its own DECbridge 90.

2–4 Configuring the DECbridge 90

Figure 2–3 shows a configuration for a work group with more than 200
stations.
Figure 2–3 Work Group With More Than 200 Stations

Ethernet Backbone

WGB

WGB
Work Group

System

< 200
S tati ons

If there are more than 200 stations in a wo r k g r o u p ,
separate into two work groups.
LJ-02229-TI0

•

Redundant connections to the backbone
If two DECbridge 90 units are configured into a redundant connection to the
backbone, the spanning tree algorithm will allow only one bridge to forward
traffic at a time. However, if a failure occurs in the backbone that causes the
connection to be separated into two LANs, the spanning tree may reconfigure
to pass all backbone traffic through your work group. When this occurs, the
work group side of the bridge may see more than 200 stations and enter flood
mode.

Configuring the DECbridge 90 2–5

Figure 2–4 shows redundant connections to the backbone.
Figure 2–4 Redundant Connections

E ther n e t B a c k b o n e

B ri d g e

W GB
W o rk G ro u p

S ystem

System

P ar allel c o n fi g u ra ti o n s .

LJ-02232-TI0

•

Bridges in the work group
If there are additional bridges on the work group side of the DECbridge 90,
be sure to count the stations on all LANs in the work group against the 200station limit and count each bridge as two against the total. In addition, if
any of these bridges lead back to the backbone, the redundant connection may
lead to spanning trees that exceed 200 stations on the work group side of the
DECbridge 90.

2–6 Configuring the DECbridge 90

Figure 2–5 shows bridges in the work group.
Figure 2–5 Bridges in Work Group

W or k Gr o u p

W GB
Backbone

WGB
Wo rk G ro u p

S ystem

S ys t e m

B r id g e in wo rk g ro u p .
LJ-02233-TI0

•

Number of bridges
The number of bridges between any two stations is limited to seven or less.
This guideline for networks with typical packet traffic loading is a compromise
of the many different protocols offered and used on Ethernet and IEEE 802.3
LANs.

Configuring the DECbridge 90 2–7

Figure 2–6 shows multiple bridges in the work group.
Figure 2–6 Multiple Bridges in a Work Group
Eth e r n e t Ba c k b o n e

Station
Bridge

Br id g e

Bridge

Br id g e

Bridge

WG B

Sta tio n

B r i dg e

Bridge

M o r e t ha n s e v e n br i dge s be t w e e n s t a t ions
on the Network.
LJ-02236-TI0

2–8 Configuring the DECbridge 90

3
Installation
Before you install the DECbridge 90 unit, it is recommended that you read this
entire manual to become familiar with the features and configuration rules and
guidelines of the DECbridge 90. If problems occur during installation, refer to
Chapter 5, Troubleshooting. Appendix A, Specifications and Parts List, provides
additional information that may be useful during installation.
The DECbridge 90 may be installed on a desk top or table, mounted on a wall by
its back cover, or installed in the DEChub 90 backplane. The only tool required
for installation is a screwdriver. The screwdriver is used to remove the back
cover, which covers the backplane connector and mounting assembly, and to
mount the bridge or the power supply on the wall.

Power Supply
The power supply (used only in standalone installations) is intended to be
wall-mounted but may be used as a floor unit. The auto-ranging power supply
supports voltages worldwide when the proper ac power cord is used. The ac
power cord and its length will vary depending on the country package ordered.

Installation 3–1

Site Considerations
The DECbridge 90 and its power supply can be placed in various locations,
including office areas, computer rooms, or wiring closets, as long as the
environmental requirements are met. These requirements are provided in
Table A–2 in Appendix A.
To install the DECbridge 90 on a desk top or table, make sure that the air
circulation around the DECbridge 90 does not become obstructed by papers
or other materials. The DECbridge 90 is convectively cooled and requires a
minimum of 10 centimeters (4 inches) of space at both ends for adequate air flow.

Standalone Installation
To install the DECbridge 90 as a standalone installation, use the DECbridge 90
kit, order number DEWGB-AA. The kit contents are listed in Appendix A.
Note
The ThinWire ports of the DECbridge 90 are not terminated internally.
External 50-ohm terminations are required.

When you choose a location, make sure that the power supply can be placed
within 1.8 meters (6 feet) of the DECbridge 90 and that the distance from the
power supply to the ac outlet does not exceed 2.4 meters (8 feet).
Figure 3–1 shows the DECbridge 90 in a standalone installation.

3–2 Installation

Figure 3–1 Standalone Installation

S wi t c h
S el ec t i on

LJ-00068-TI0

Mount DECbridge 90 on a Wall
To install the DECbridge 90 as a standalone unit, refer to Figure 3–1 and follow
this procedure:
1. Remove the back cover of the DECbridge 90 (Figure 3–2).
a. Insert a small screwdriver into the top mounting hole in the cover.
b. Lift up on the latch and pull the top of the cover away and down from the
unit.
2. Use the mounting holes on the cover to determine the placement for the
mounting screws on the wall.
3. Attach the screws to the wall, leaving enough clearance to hang the bridge.

Installation 3–3

4. Attach the cover to the bridge and hang the unit on the wall.
Figure 3–2 Removing the Back Cover

LJ-00320-TI0

3–4 Installation

Make Connections for Standalone Installations
AUI Backbone Connection
Select the AUI backbone connection by sliding the ThinWire/AUI selector switch
on the front panel toward the backbone port AUI connector.
When the AUI port is attached to a 10Broad36 modem, the modem should be
configured for local echo of transmissions.
To connect the transceiver cable, follow this procedure:
1. Push the slide latch to the unlocked position.
2. Plug the transceiver cable into the connector.
3. Push the slide latch down until it snaps into the locking position, to secure
the connector (Figure 3–3).
4. Gently pull on the cable to make sure that the latch is secure.
Note
The DECbridge 90 does not detect a collision presence test failure in the
transceiver that is connected to the AUI port.

Installation 3–5

Figure 3–3 shows the proper connection of the transceiver cable.
Figure 3–3 Connecting Transceiver Cables

Push the Slide Latch
Down Until it Snaps
Into the Locking
Position, Securing
the Connector

LJ-02157-TI0

ThinWire Backbone Connection
Select the ThinWire connection by sliding the ThinWire/AUI selector switch on
the front panel toward the backbone port ThinWire connector. When you connect
to the ThinWire cable, make sure that the cables are properly terminated. Refer
to Figure 3–4 and Figure 3–5 for guidelines on terminating cables.

3–6 Installation

Figure 3–4 shows how to connect to the middle of a ThinWire segment.
Figure 3–4 Connecting to the Middle of a ThinWire Segment

Station A

Station B

Work Group Bridge

S ta t i o n C

LJ-00243-TI0

Figure 3–5 shows how to connect to the end of a ThinWire segment.
Figure 3–5 Connecting to the End of a ThinWire Segment

St at i on A

St at io n B

Sta tio n C

Wo rk Gro u p B r i dge

LJ-00242-TI0

Work Group Connection
Connect the work group by attaching a segment of ThinWire cable to the
ThinWire connector on the DECbridge 90.
When connecting to a ThinWire cable, make sure that the cables are properly
terminated (Figure 3–4 and Figure 3–5).
Power Supply Connection
To connect the power supply to the DECbridge 90, place the power supply within
1.1 meters (4.3 feet) of the DECbridge 90, and follow this procedure:
1. Attach the ac power cord to the power supply.
2. Plug the power supply into an ac outlet.
The DECbridge 90 will run a 10-second self-test during which all front panel
lights will turn on.
On successful completion of the test, the following lights will remain on: DC
OK, System Port OK, Work Group Port OK, and Backbone Port OK. The
Bridge Forwarding State indicator will remain on for 30 seconds as the bridge
learns the network configuration, and then the indicator will turn off.
Refer to Chapter 5, Troubleshooting, if the DECbridge 90 indicators do not
turn on.

Installation 3–7

Backplane Installation
To install the DECbridge 90 in the DEChub 90 backplane, use the DECbridge 90
kit, order number DEWGB-MA. The kit contents are listed in Appendix A.
Figure 3–6 shows the DECbridge 90 in a DEChub 90 backplane.
Figure 3–6 Installing the DECbridge 90 into DEChub 90 Backplane Slot 8

LJ-02081-TI0

3–8 Installation

Install the DECbridge 90 in the DEChub 90 Backplane
To install the DECbridge 90 in the DEChub 90 backplane, refer to Figure 3–6 and
follow this procedure:
1. Remove the back cover of the DECbridge 90.
a. Insert a small screwdriver into the top mounting hole in the cover.
b. Lift up on the latch with the screwdriver and pull the top of the cover
away and down from the unit.
2. Place the lower mounting tab, located on the back of the DECbridge 90, into
slot 8 of the backplane.
3. Rock the bridge into place. You will hear a click when the bridge is secured in
the slot.

Make Connections for Backplane Installations
1. Select the AUI or ThinWire connection by sliding the AUI/ThinWire selector
switch on the front panel toward the backbone port AUI or ThinWire
connector.
When the AUI port is attached to a 10Broad36 modem, the modem should be
configured for local echo of transmissions.
2. Make the selected backbone connection (AUI or ThinWire). Refer to the Make
Connections for Standalone Installations section, for information about how
to connect the transceiver cables.
The work group port is automatically connected once the DECbridge 90 is
installed in the DEChub 90 backplane. The backplane provides power to the
bridge; therefore, no other power supply is needed. Any other unit installed
in the backplane is bridged automatically and is part of the work group.
3. Power up the backplane if power is not already on.
The DECbridge 90 will run a 10-second self-test during which all front panel
lights will turn on.
On successful completion of the test, the following indicators will remain
on: DC OK, System Port OK, Work Group OK, and Backbone Port OK. The
Bridge Forwarding State indicator will remain on for 30 seconds as the bridge
learns the network configuration, and then the indicator will turn off.
Refer to Chapter 5, Troubleshooting, if the DECbridge 90 indicators do not
turn on.

Installation 3–9

4
Managing the DECbridge 90
The DECbridge 90 unit is managed by Maintenance Operations Protocol (MOP),
which allows advanced bridge features, such as protocol filtering, to be set up
without any additional management software. Host system support, which is
standard on all VMS installations, is required for MOP console carrier operation.
On ULTRIX installations, the MOP option is a separate utility that may be
installed from the original distribution media.
The DECbridge 90 also supports Remote Bridge Management Software (RBMS).
RBMS allows similar bridge management through the use of additional Digital
management software. Refer to the Remote Bridge Management Software section
in this chapter for further information.

DECbridge 90 Operation
The DECbridge 90 is a packet store-and-forward device that receives all
IEEE 802.3 and Ethernet packets and, if necessary, forwards them from one port
to the other. This capability enables the bridge to isolate high-traffic areas from
the rest of the LAN. For example, if the systems and servers in a cluster usually
communicate with each other and rarely communicate with other systems on the
LAN, the bridge keeps that traffic local, that is, off the main LAN.
The decision to filter or forward packets is determined by the packet’s destination
address or protocol type as follows:
•

Destination Address Filtering - The bridge, on receiving a packet, scans
its address database, which contains node addresses from the work group
port that are dynamically learned by the bridge. The destination address
of the packet is compared with known addresses in the work group. If no
protocol-type filters are enabled for the packet, the bridge makes its decision
to filter the packet based on the destination address. Otherwise, the packet is
subjected to protocol-type filtering.

•

Protocol Filtering - The bridge may be configured to filter selected protocols
so that user-selected protocols can be isolated within or outside a specific
work group.

Managing the DECbridge 90 4–1

•

Flood Mode - The bridge forwards all packets from the backbone to the work
group subject only to protocol filtering. When flood mode is disabled, a station
in the work group must have its address in the address table to receive
messages from the backbone LAN. When flood mode is enabled, the backbone
traffic is forwarded to the work group subject only to the protocol filters, and
not subject to the address filters. This is useful in the following situations:
–

A work group that exceeds 200 stations cannot be accommodated in the
DECbridge 90 address table. Flood mode allows full connectivity with
more than 200 stations by eliminating the automatic traffic isolation
between the work group and the backbone LANs.

–

If a station in the work group does not transmit messages before the
address age time expires, or if the station never transmits, it will not be
in the address table. Flood mode must be enabled to reach these stations
from the backbone LAN. Flood mode will be enabled automatically
whenever the DECbridge 90 detects more than 200 stations in the work
group. When enabled automatically, it will also be disabled automatically
approximately 10 minutes after the bridge discovers that the work group
no longer exceeds the 200-station limit.

Flood mode can be enabled or disabled manually by using the SET BRIDGE
command. When enabled manually, flood mode remains enabled regardless
of the work group size. Refer to the Description of Commands section in
this chapter for information about the SET and DEFINE BRIDGE FLOOD
DISABLE commands.
Flood mode reduces the traffic isolation features of the bridge; therefore, it
should be enabled only when necessary.

DECbridge 90 Functions
•

Protocol-transparent, multivendor communications - The DECbridge 90
provides connectivity between two network segments regardless of vendor
hardware or software, provided that the hardware and software conform to
IEEE 802.3 and Ethernet compliance requirements.

•

Connectivity - The DECbridge 90 can be used on both IEEE 802.3 and
Ethernet networks.

•

Backbone connection - The DECbridge 90 provides switch-selectable AUI
or ThinWire connection to the backbone.

•

Automatic self-test - The DECbridge 90 automatically initiates a 10-second
self-test of the basic functions of the DECbridge 90 when the bridge is
powered up.

4–2 Managing the DECbridge 90

•

Online diagnostics - The DECbridge 90 has automated continuous testing
of the DECbridge 90 hardware.

•

Loop detection - The DECbridge 90 determines if there are any loops by
communicating with other Digital or IEEE 802.1 compliant bridges in the
network and it configures appropriately to eliminate loops.

Spanning Tree Algorithm
The spanning tree is an automatic process used by all bridges in an extended
LAN configuration to create a logical, loop-free network. The spanning tree
is determined automatically by an algorithm resident in each bridge. No user
action or network management is required to configure the network. If a loop
is detected, the process computes and implements a loop-free network topology.
This process prevents packets from circulating through the network indefinitely.

Spanning Tree Algorithm Properties
Although the bridges in an extended network can be placed in an arbitrary
fashion, the logical network that bridges automatically create (due to the
algorithm) is always a spanning tree with the following properties:
•

No loops

•

Only one path between any two bridges

•

All LANs are connected

Refer to the Bridge and Extended LAN Reference for detailed information about
the spanning tree process.

MOP
Maintenance Operations Protocol (MOP) is a host-based protocol. Console carrier
is a component of MOP that accesses the user interface command language
embedded in the DECbridge 90. Console carrier provides the ability to establish
a single conversational terminal line link between a terminal or workstation on
the LAN and the DECbridge 90. This link transmits and receives keystrokes.

MOP Functions
MOP console carrier management allows you to perform the following functions:
•

Examine the bridge characteristics of address entry age, forwarding state,
firmware version, name of flash ROM image, and uptime.

•

Examine the port characteristics of backbone and work group ports (hardware
address, MOP counters, and bridge counters).

Managing the DECbridge 90 4–3

•

Examine port status (management connected, management disconnected,
properly operating, or broken) of both bridge ports and of repeater ports that
share the DEChub 90 backplane with the bridge.

•

Examine the work group address database entries 1 to 200.

•

Examine the current or permanent protocol filter entries 1 to 16.

•

Set protocol filters.

•

Reset the bridge.

•

Connect or disconnect a port (work group or backbone, or repeaters in the
backplane).

•

Set the bridge maximum address entry age, current or permanent.

•

Define the bridge password.

•

Enable and disable flood mode.

Refer to the Description of Commands section in this chapter for additional
information about command syntax.

Accessing MOP from VMS Systems
On a VMS operating system, the MOP console carrier is included as part of the
Network Control Program (NCP) facility, which requires a DECnet license.
You do not need increased user privileges to use NCP. To establish a console
carrier session, you must know the following:
•

The Ethernet address of the bridge that is to be managed

•

The Ethernet name of the circuit that contains the bridge

A VMS system may have more than one Ethernet interface; therefore, the
circuit name is needed. The Ethernet address can be found on the label on the
DECbridge 90 front panel. The following Ethernet circuit names, based on system
type, apply:

4–4 Managing the DECbridge 90

Table 4–1 Ethernet Circuit Names for Systems
System

Circuit Name

VAX 6000 and VAX 9000 XMI computers

mna-0

BI-based systems (VAX 6300 and VAX 6400 computers)

bna-0

VAX 4000 computer series

isa-0

MicroVAX systems and VAX 3600 and VAX 3900
computers

qna-0

VAXstation 2000 and VAXstation 3000 computer series

sva-0

VAX–11/780 and VAX–11/785 computers (UNIBUS)

una-0

Example:
If the bridge address is 08-00-2B-01-23-45 and the Ethernet circuit name is sva-0,
a typical VMS command line to establish the session from a VAXstation 3100
system is:
$ MCR NCP CONNECT VIA SVA-0 PHYSICAL ADDRESS
08-00-2B-01-23-45
When you have established connection, the following appears on the screen:
Console connected (press CTRL/D when finished)
Accessing a Bridge Repeatedly
If you need to access a specific bridge repeatedly, you can enter the Ethernet
address for that bridge in the NCP database. This is usually done by choosing an
arbitrary address in area 13. Bridge names entered in the NCP database may be
a maximum of six characters.
Example:
If you call your bridge DBRG1 on address 13.87 and access it from a VAX 6400
system (where the Ethernet circuit name is bna-0), you can use the following
commands:
$ NCP
NCP> DEFINE NODE DBRG1 ADDRESS 13.87 HARDWARE
08-00-2B-01-23-45 - SERVICE CIR BNA-0
NCP> SET NODE DBRG1 ALL
You can then enter the following:
$ NCP CONNECT NODE DBRG1

Managing the DECbridge 90 4–5

Accessing MOP from ULTRIX Systems
On the ULTRIX operating system, the console carrier is a separate utility
included as part of the MOP option. This option is part of the regular
distribution, however, it is not selected by default and is not included in the
basic installation. You can install the MOP from the original distribution media
using the setld utility. You must have superuser privileges to invoke the console
carrier.
Once the MOP option is installed, each bridge to be managed must be given a
name and a dummy node number using the addnode utility. For example:
# addnode 13.1 DBRG1
Once the name and node number are assigned, you can establish the link at any
time using the ccr command:
# ccr -n DBRG1 -h 08-00-2B-01-23-45 -c sva-0
In this example, the -h qualifier is followed by the station address of the
DECbridge unit to be attached. The -c qualifier is followed by the name of
the Ethernet circuit to use for the connection. Ethernet circuit names, based on
system type, apply. Refer to Table 4-1 for circuit names.
When you have established connection, the following appears on the screen:
Console connected (press CTRL/D when finished)

Console Carrier User Interface
The DECbridge 90 is not shipped with a preset password; therefore, no password
prompt appears when you connect for the first time. For secure operation of
the DECbridge 90, you should define a password using the DEFINE BRIDGE
PASSWORD command.
The password prompt is represented by the pound sign (#). If you do not define a
password, then the password prompt does not appear when you log in.
You have three attempts to enter a password. If all three attempts fail, then you
must disconnect and try again.
If you have defined a password for the DECbridge 90, then the following appears
on the screen after the network connection to the bridge is established:
Console connected (press CTRL/D when finished)
#
You must now enter the bridge password to access the console carrier. The
password you enter will not appear on the screen.

4–6 Managing the DECbridge 90

After you successfully enter the password, or if no password is defined, the
following appears on the screen:
DEWGB V2.0 08-00-2B-2D-9B-81 © Digital Equip Corp
FPROM V2.5f ©1991,92 Digital Equip Corp 25-JUN-92
DECbridge>

Console Carrier Command Language
With the exception of the help facility, the console carrier command language is
similar to the DECserver command language. Type a question mark (?) at any
point in the command line to see a list of the options that are available to you at
that point in the command line. Unique abbreviations of commands are accepted.
The command options are:
DEFINE
DISPLAY
LIST
SET
SHOW
TEST (for manufacturing use only)
Table 4–2 provides a summary of the DECbridge 90 commands.
Table 4–2 Summary of DECbridge 90 Commands
Command
1

DEFINE

Argument and Parameter
BRIDGE AGE age
BRIDGE FLOOD
ENABLE
DISABLE
BRIDGE HUB_MANAGEMENT
ENABLE
DISABLE
BRIDGE PASSWORD
BRIDGE SPANNING TREE
ENABLE
DISABLE

1
Changes made with the DEFINE command change only the default settings, which are assumed on
power up or reset. DEFINE commands do not change the currently active values.

(continued on next page)

Managing the DECbridge 90 4–7

Table 4–2 (Cont.) Summary of DECbridge 90 Commands
Command

Argument and Parameter
PORT port number
ENABLE
DISABLE
PROTOCOL protocol number
FILTER ALL protocol identifier
FILTER BACKBONE protocol identifier
FILTER GROUP protocol identifier
FILTER WORKGROUP protocol identifier
FORWARD protocol identifier
NONE

DISPLAY

No arguments or parameters are needed

LIST

BRIDGE
PROTOCOL protocol number

SET

ALL
BRIDGE AGE age
BRIDGE FLOOD
ENABLE
DISABLE
BRIDGE RESET
BRIDGE HUB_MANAGEMENT
ENABLE
DISABLE
BRIDGE SPANNING TREE
ENABLE
DISABLE
PORT port number
ENABLE
DISABLE
PROTOCOL protocol number
FILTER ALL protocol identifier
FILTER BACKBONE protocol identifier
FILTER GROUP protocol identifier
FILTER WORKGROUP protocol identifier
FORWARD
NONE

The SET commands change only the currently active values, but do not affect the defaults that are
assumed on power up or reset.

(continued on next page)

4–8 Managing the DECbridge 90

Table 4–2 (Cont.) Summary of DECbridge 90 Commands
Command

Argument and Parameter
REPEATER

SHOW

ADDRESS start index
BRIDGE
PORT port number
PROTOCOL protocol number
REPEATER hub slot number

Description of Command Parameters
An address number is an index into the work group address database. The valid
range is 1 to 200.
An age is an address database lifetime entry. The valid range, in seconds, is 0 to
32767.
A hub slot number is a single number, in the range of 1 to 8, that identifies a
hub slot containing a DECrepeater 90. When two DEChub units are connected
together, a hub slot number is a pair of numbers; the first is the hub number of 1
to 2, and the second is the slot number within the hub of 1 to 8. For example, the
numbers 2,4 designate the fourth slot from the left, in the second DEChub, which
is the hub that does not contain the DECbridge 90.
A password string is a string of up to 16 characters.
A protocol identifier is a string of either two hex digit pairs (60-00) to specify an
Ethernet protocol, or a string of five hex digit pairs (08-00-2B-60-00) to specify an
IEEE 802.3 SNAP SAP protocol ID.
A protocol number is a decimal index into the protocol database. The valid range
is 1 to 16.
A port number is either a DECbridge 90 port, or the number of a port on a
repeater installed in the DEChub backplane with the bridge. The DECbridge
backbone port is the single digit 1. The work group port is 2. A repeater port is
identified by a hub slot number as described above, and the port number within
the slot of 0 to 8. For example, 2,4 designates the fourth port on a repeater in
slot 2, in the same hub as the DECbridge 90. The numbers 2,4,1 refer to the first
port on a repeater in the fourth slot of the second hub.

Managing the DECbridge 90 4–9

Description of Commands
The following section describes the DECbridge 90 commands. The commands are
listed in alphabetical order.
DEFINE BRIDGE AGE age
SET BRIDGE AGE age
Changes the maximum allowable age of an address entry. An address in the
work group address database will be removed if no messages are received from
the node for the amount of time specified by the age. The age parameter is in
seconds. Setting the age to 0 will prevent any addresses from being removed.
These addresses will remain until the bridge is powered down or reset.
Changes made with the DEFINE command will survive a reset or power failure;
changes made with the SET command will not.
DEFINE BRIDGE FLOOD DISABLE
SET BRIDGE FLOOD DISABLE
Disables flood mode in the DECbridge 90. Attempting to disable flood mode
with a work group larger than 200 stations (that is, when the Work Group Size
Exceeded light is on) will not be successful.
Flood mode is a feature that, when enabled, does not filter traffic from the
backbone to the work group based on destination address. All messages that pass
protocol filters are passed to the work group, regardless of destination address.
This feature is useful when a station within the work group is not receiving
messages from the backbone for either of the following reasons:
a. The station has not transmitted any packets, therefore, the bridge is unaware
that the station exists within the work group.
b. The bridge is unaware of the station because the 200-station work group limit
has been exceeded. In this case, flood mode is automatically enabled and all
stations in the work group will be able to receive packets from the backbone.
When enabled, flood mode disables destination address filtering and introduces
more traffic into the work group. However, protocol filtering will still be in effect
and packets from the work group will still be subject to full filtering when passing
to the backbone.

4–10 Managing the DECbridge 90

DEFINE BRIDGE FLOOD ENABLE
SET BRIDGE FLOOD ENABLE
Enables flood mode in the bridge. Refer to the DECbridge 90 Operation section
and the previous flood commands for a description of flood mode.
DEFINE BRIDGE HUB_MANAGEMENT DISABLE
SET BRIDGE HUB_MANAGEMENT DISABLE
Disables all repeater management through the DECbridge 90 unit for
DECrepeater 90 units in the DEChub 90 backplane. When disabled, you will
not be able to use SHOW REPEATER, SET PORT, or SHOW PORT commands
on repeater ports, and you will not get port number information from the SHOW
ADDRESS command.
DEFINE BRIDGE HUB_MANAGEMENT ENABLE
SET BRIDGE HUB_MANAGEMENT ENABLE
Reverses the effect of the SET or DEFINE BRIDGE HUB_MANAGEMENT
DISABLE commands.
DEFINE BRIDGE PASSWORD
SET BRIDGE PASSWORD
Changes the password string. You are prompted twice for a new password. The
password may be up to 16 characters long and is not displayed on the screen.
This change will survive a reset. There is no corresponding SET command.
MOP provides a mechanism for setting and checking passwords. This mechanism
is only intended to provide protection against accidental tampering with
parameters and is not intended as a security feature. No attempt is made to
prevent compromise of the password by malicious users. The DECbridge 90
should not be used in applications that absolutely depend on the prevention of
any unauthorized modifications to the parameters.

Managing the DECbridge 90 4–11

DEFINE BRIDGE SPANNING_TREE DISABLE
SET BRIDGE SPANNING_TREE DISABLE
Disables the use of the bridge spanning tree autoconfiguration algorithm for
your DECbridge 90 unit and prevents forwarding of any spanning tree network
messages. If spanning tree is disabled, the DECbridge 90 will not detect loops
in the network bridge topology. If a loop is configured while the spanning tree
algorithm is disabled, the network will be quickly saturated by the forwarding
of messages around this loop. For this reason, Digital Equipment Corporation
recommends that the spanning tree algorithm be enabled at all times.
DEFINE BRIDGE SPANNING_TREE ENABLE
SET BRIDGE SPANNING_TREE ENABLE
Reverses the effect of the SET or DEFINE BRIDGE SPANNING_TREE DISABLE
commands.
DEFINE PORT port number DISABLE
SET PORT port number DISABLE
Disables the ability to forward packets through the bridge by disabling the
specified port. The DEFINE command changes only the nonvolatile database;
the SET command changes only the current state. Both ports must be enabled
before the bridge can begin forwarding messages. The port numbers are 1 for the
backbone port, and 2 for the work group port.
DEFINE PORT port number ENABLE
SET PORT port number ENABLE
Reverses the effect of the SET or DEFINE PORT DISABLE command. Both ports
must be enabled before the bridge can begin forwarding. In new units, the ports
default to enabled.
DEFINE PROTOCOL protocol number FILTER ALL protocol identifier
SET PROTOCOL protocol number FILTER ALL protocol identifier
Sets the specified protocol identifier to be one of a limited number of protocol
types that are filtered, where all others are forwarded. All messages of the given
protocol identifier are filtered. (Refer to Table 4–3 for a list of the protocol type
codes and names.) If this command is accepted, the bridge invert protocol filter
mode is disabled, and the SET PROTOCOL FORWARD command may no longer
be used until all of these entries are deleted with the SET PROTOCOL NONE
command.

4–12 Managing the DECbridge 90

DEFINE PROTOCOL protocol number FILTER BACKBONE protocol identifier
SET PROTOCOL protocol number FILTER BACKBONE protocol identifier
Sets the specified protocol type such that messages individually addressed to
stations are forwarded, and group-addressed messages from the work group port
are forwarded; however, group-addressed messages of this protocol will not enter
the work group from the backbone. This command is not affected by the bridge
invert protocol filter mode.
DEFINE PROTOCOL protocol number FILTER GROUP protocol identifier
SET PROTOCOL protocol number FILTER GROUP protocol identifier
Sets the specified protocol type such that messages individually addressed to
stations are forwarded; however, broadcast and group-addressed messages of this
protocol are filtered. This command is not affected by the bridge invert protocol
filter mode.
DEFINE PROTOCOL protocol number FILTER WORKGROUP protocol
identifier
SET PROTOCOL protocol number FILTER WORKGROUP protocol identifier
Sets the specified protocol type such that messages individually addressed to
stations are forwarded, and group-addressed messages from the backbone port
are forwarded; however, group-addressed messages of this protocol will not enter
the backbone from the work group. This command is not affected by the bridge
invert protocol filter mode.
DEFINE PROTOCOL protocol number FORWARD protocol identifier
SET PROTOCOL protocol number FORWARD protocol identifier
Sets the specified protocol type to be one of a limited number of protocol types
that are forwarded, where all others are filtered. If this command is accepted,
the bridge is placed into the bridge invert protocol filter mode. This means
that the SET PROTOCOL FILTER ALL command may no longer be used until
all forwarded protocol entries are removed. Use the SET PROTOCOL NONE
command to delete protocol filters. Generally, use the SET PROTOCOL FILTER
ALL command to stop unwanted protocols rather than to list explicitly the
permitted protocols.

Managing the DECbridge 90 4–13

DEFINE PROTOCOL protocol number NONE
SET PROTOCOL protocol number NONE
Deletes a protocol filter entry from the protocol filter database. Note that if the
last FORWARD protocol is deleted, the bridge will go back to forwarding all
protocols.
DISPLAY
The continuous port counter display toggles on and off. The screen is cleared and
the numbers are re-displayed every 10 seconds thereafter, until the DISPLAY
command is issued again. The DISPLAY command output appears as follows:
DECbridge 08-00-2B-1E-2C-0F Uptime: 109,929.66 seconds
System buffer unavailable: 0
Work group size exceeded: 0
Backbone side:
Work group side:
Frames received: 266,788
Frames received: 3,233
Relayed to work group: 178,640
Relayed to backbone: 1
Received frame too long: 0
Received frame too long: 0
Frames sent: 7
Frames sent: 182,476
Sent, initially deferred: 1
Sent, initially deferred: 96
Sent, single collision: 0
Sent, single collision: 2
Sent, multiple collisions: 0
Sent, multiple collisions: 0
Unsent, excessive collisions: 0
Unsent, excessive collisions: 0
Unsent, carrier check failed: 0
Unsent, carrier check failed: 0
Unsent, lifetime exceeded: 0
Unsent, lifetime exceeded: 0
Received block check error: 0
Received block check error: 0
Received framing error: 0
Received framing error: 0
Unsent, remote failure to defer: 0
Unsent, remote failure to defer: 0
DECbridge>
LIST BRIDGE
Displays the nonvolatile bridge-wide parameters.
LIST PROTOCOL protocol number[, protocol number]
Shows either "unused," or the protocol type value, for every entry in the
nonvolatile protocol database. This filter becomes the active filter when the
DECbridge 90 is reset.

4–14 Managing the DECbridge 90

SET ALL
Resets the protocol filters and bridge-wide parameters from the nonvolatile
database. This affects maximum age, preforwarding/blocking delay, all protocol
filters, and port state.
SET BRIDGE RESET
Performs the equivalent of turning the bridge off and back on again.
SET PORT [hub number,] slot number, port number DISABLE
Disables the attachment of a specific repeater port in the DEChub backplane.
The port status indicator on the selected DECrepeater will flash, indicating
that the port was disconnected by the network manager. There is no equivalent
DEFINE command for disabling repeater ports. Disabling port 0 on a repeater
will disconnect the repeater from the hub.
SET PORT [hub number,] slot number, port number ENABLE
Reverses the effect of SET PORT DISABLE for DECrepeater 90 ports.
SHOW ADDRESS [start index[, stop index]]
Displays the station address for the selected range of entries in the address
database. The indexes range from 1 to 200. The start index is always displayed;
other entries in the range are only displayed if they are not empty. Addresses
in this database are all in the work group. If indexes are omitted, the addresses
of all stations in the work group are listed. When the DECbridge 90 is used
with repeaters, the hub slot number and repeater port to which each station is
attached are also displayed. Note that it may take several minutes for the SHOW
ADDRESS command to accurately reflect the correct repeater port number for
stations recently added to the network or moved from one port to another.
SHOW BRIDGE
Displays bridge firmware revision numbers, station address, uptime, current
maximum age, current console carrier owner, bridge state, system buffer
unavailable count, work group size, the number of times the flash EPROM has
been erased, flood mode status, and all bridge-wide spanning tree parameters.

Managing the DECbridge 90 4–15

The bridge states are listed in the following table:
Bridge State

Meaning

1F,3F

Forwarding, flood mode enabled

17,37

Forwarding

16,36,1E

Preforwarding

15,35,1D

Blocking (configuration error)

12,32,1A

Disabled (one or both ports disabled)

13,33,1B

Broken (one or both ports failing loopback test)

The first digit is 1 when the bridge state is normal. If the first digit is 3, then the
bridge is using invert protocol filter mode. If the last digits are A through F, then
flood mode is physically enabled.
Note
When flood mode is automatically enabled after the 200 station limit
is reached, it will not be reflected in the user flood mode status in the
SHOW BRIDGE command. It will, however, be reflected in the bridge
state.

Refer to the DEFINE PROTOCOL command descriptions for more details.
SHOW PORT port number
Displays all the MOP counters, bridge counters, and spanning tree state kept by
the DECbridge 90. Port 1 is the backbone port; port 2 is the work group port.
The spanning tree port states are listed in the following table:
Port State

Meaning

Disabled

Listening

Learning

Forwarding

Blocking

Broken

4–16 Managing the DECbridge 90

SHOW PORT [hub number,] slot number, port number
Shows whether the port is enabled or disabled and shows the operational status
of the port. Hub numbers may be 1 or 2; slot numbers may be 0 to 8. For
the DECrepeater 90T, port numbers are 0 to 8; for the DECrepeater 90C, port
numbers are 0 to 6, for the DECrepeater 90A, port numbers are 0 and 1.
SHOW PROTOCOL [start number[, stop number]]
Shows either EMPTY, or the current protocol type, value, and current forwarding
status of each entry in the range given. Numbers range from 1 to 16. If numbers
are omitted in the command, all 16 protocol filters are displayed. The LIST
command shows the filters that are loaded when the DECbridge 90 is reset.
SHOW REPEATER [[hub slot number,] slot number]
Shows the type of repeater and the port status for each port on that repeater.
The hub number may be 1 or 2, and slot numbers are in the range of 1 to 8. If no
parameters are given, the status is displayed for all repeaters in both hubs.
TEST test number
Invokes a set of self-tests (manufacturing use only).

Protocol Filtering Examples
The following examples show some of the ways protocol filtering can be used with
the DECbridge 90. Table 4–3 lists some of the Digital Ethernet protocol type
codes that are used to establish protocol filters.
Table 4–3 Protocol Type Codes and Names
Type Code

Name

60-01

MOP remote boot

60-02

MOP console carrier, counters, and system identification

60-03

DECnet

60-04

LAT

60-05

Diagnostics

60-06

Customer-specific

60-07

Local Area VAXcluster

80-38

Bridge management

Managing the DECbridge 90 4–17

Example 1: Keeping VAXcluster traffic out of your work group.
If you have an entire Local Area VAXcluster (LAVc) on the work group side of the
DECbridge 90, you can define the filtering with the following command:
DECbridge> DEFINE PROTOCOL 0 FILTER ALL 60-07
This prevents any cluster traffic from entering or leaving the work group.
Specifically, this means your cluster traffic will not be seen on the backbone, and
no other cluster traffic will be seen on your own work group.
If the external cluster traffic is substantial, this could improve your local network
performance. This also makes it more difficult for others on the network to
monitor your cluster traffic and eliminates the need to make your cluster ID
different from others on the same extended LAN.
Example 2: Keeping boot requests of other groups out of your group.
MOP remote boot requests come from LAVc satellite systems, DECserver terminal
servers, VAXELN systems, and other sources, when they need to have their
software reloaded from a boot server. Boot request messages begin with groupaddressed messages. If line service is enabled in NCP, this creates extra processes
on VMS systems which, if your node is not a designated boot node for the
requester, slow down your system. This is particularly true after a building-wide
power shutdown. It is desirable to filter out these boot requests but still be able
to boot nodes in your own work group.
To stop all boot requests enter the following command:
DECbridge> DEFINE PROTOCOL 1 FILTER ALL 60-01
This command would not work if you had DECserver terminal servers or other
systems inside your work group, and the designated boot servers are outside
your work group. To accommodate this situation, you can enter the following
command:
DECbridge> DEFINE PROTOCOL 1 FILTER BACKBONE 60-01
Now nodes inside your work group may issue boot requests and have them
forwarded to a boot server outside the work group. Additionally, the boot requests
from outside will be blocked at the bridge and will not slow down nodes inside the
work group.

4–18 Managing the DECbridge 90

Example 3: Controlling LAT access
The LAT protocol uses a group-addressed message for service nodes to announce
their availability to the DECserver units. The one-way group address filter in the
bridge allows additional control to access nodes in the work group. To allow users
in your work group to access all network-wide services but to limit access within
the work group to only those servers that are in the same work group, enter the
following command:
DECbridge> DEFINE PROTOCOL 2 FILTER WORKGROUP 60-04
Service announcements that are generated by nodes in the work group are
blocked by the DECbridge, and will not be seen by DECserver units on the rest
of the network. Service announcements arriving from the outside network are
allowed into the work group; therefore, your own servers can still connect to
services offered by others.

Remote Bridge Management Software (RBMS)
RBMS is a Digital proprietary network management protocol which, similar
to MOP, allows the bridge to be managed remotely. Unlike MOP, however,
RBMS is neither directly accessible nor visible to the user. RBMS is used by
the DECagent 90 management agent, DECmcc management software, and other
Digital products. The DECagent 90 uses RBMS to provide Simple Network
Management Protocol (SNMP) management of the bridge. DECmcc provides a
user interface to complex network management tasks.
A detailed discussion of RBMS features is beyond the scope of this manual; the
user needs only to be aware that the DECbridge 90 may be managed by software
using the RBMS protocol. Refer to Appendix B, Related Documentation, for
further information about ordering the Remote Bridge Management Software
Guide.

Managing the DECbridge 90 4–19

Error Messages
Table 4–4 describes the DECbridge 90 error messages.
Table 4–4 DECbridge 90 Error Messages
Error Message

Description

Address n: unused address

Indicates that the address number n does not contain
a station address.

Confirmation error - password
not changed

Indicates that the second entry or verification of
the new password given to the DEFINE BRIDGE
PASSWORD command did not match the first entry.

DECbridge 90 is not the
designated hub manager

Indicates that the DECbridge 90 was not the
designated hub manager when the SHOW PORT
or SHOW REPEATER command was issued. This
occurs when:
•

The bridge is reset and, for 60 seconds, the
DECbridge 90 is not the hub manager.

•

Another DECbridge unit is acting as the current
hub manager.

•

A fault exists in the MMJ cable or connections
between two DEChub backplanes, or in the power
supply of one of the DEChub units, that prevents
repeater management communication.

EEPROM failure, SET ALL not
performed

Indicates that EEPROM did not pass the self-test
diagnostic. The DECbridge 90 unit should be serviced.
Information in the permanent configuration database
may not be valid and DEFINE commands may not
have the intended effect. The unit will continue
to operate using the default parameters, or with
parameters issued with the SET command.

Enter maximum address age
from 2 to 65534 seconds

Indicates that invalid address age was entered with
the SET BRIDGE AGE or DEFINE BRIDGE AGE
commands. Enter a number between 2 and 65534
seconds.

Ethernet protocol xx-xx or IEEE
PID xx-xx-xx-xx-xx

Indicates that the protocol type parameter entered
with the SET PROTOCOL or DEFINE PROTOCOL
command was not a sequence of either two or five
hexadecimal digit pairs.
(continued on next page)

4–20 Managing the DECbridge 90

Table 4–4 (Cont.) DECbridge 90 Error Messages
Error Message

Description

FILTER ALL protocols must
be removed before defining any
FORWARD command

Indicates an attempt to configure contradictory
protocol filtering rules in the permanent database.
Before the DECbridge 90 will accept a filter request,
you must enter the LIST PROTOCOL command to
identify protocol filters marked as FILTER ALL, and
remove them with the DEFINE PROTOCOL n NONE
command.

FILTER ALL protocols must
be removed before setting any
FORWARD command

FORWARD protocols must be
removed defining any FILTER
ALL command

Indicates an attempt to configure contradictory
protocol filtering rules in the current database. Before
the DECbridge 90 will accept a filter request, you
must enter the SHOW PROTOCOL command to
identify protocol filters marked as FORWARD, and
remove them with the DEFINE PROTOCOL n NONE
command.

FORWARD protocols must be
removed setting any FILTER
ALL

Indicates an attempt to configure contradictory
protocol filtering rules in the current database. Before
the DECbridge 90 will accept a filter request, you must
enter the SHOW PROTOCOL command to identify
protocol filters marked as FORWARD, and remove
them with the SET PROTOCOL n NONE command.

Hub management disabled

Indicates that the SHOW PORT or SHOW REPEATER
command was issued to a DECbridge 90 for
which repeater management is disabled. Enable
repeater management with the SET BRIDGE
HUB_MANAGEMENT ENABLE command before
trying again.

Hub number and slot number
[ [hub], slot]. Hub is 1 or 2, slot
is 1-15

Indicates that one or more parameters provided to the
SHOW REPEATER command was out of range. Hub
number must be either 1 or 2; slot number must be
between 1 and 15.
(continued on next page)

Managing the DECbridge 90 4–21

Table 4–4 (Cont.) DECbridge 90 Error Messages
Error Message

Description

Hub h slot s - port number out of
range

Indicates that the port number entered with the
SHOW PORT command was out of range for the
device in hub h slot s. Use the SHOW REPEATER
command to determine the number of ports for the
device, and specify a port number within that range.

Hub h slot s not a repeater

Indicates that the device does not use the same
management protocol as the DECrepeater 90C and
DECrepeater 90T; and its ports, if any, cannot be
managed by the DECbridge 90.

Hub h slot s unrecognized type

Indicates that repeater type in hub h slot s is not
known to the DECbridge 90, but the repeater ports
can still be managed with the DECbridge 90.

No repeater responds

Indicates that there is no repeater installed in the
requested hub slots, or the repeater is not functioning.

No such port

Indicates that the bridge port number entered with
the SHOW PORT command was out of the range. The
valid range is 1 to 2.

Password too long - not changed

Indicates that a password of more than 16 characters
was given to the DEFINE BRIDGE PASSWORD
command.

Port number [[hub,]slot,]port

Indicates that one of the parameters to a SET PORT
or DEFINE PORT command was not a valid hub, slot,
or port number.

Protocol type number [first [,last] ] Indicates that one or more parameters entered with
in range 1-16
the SHOW PROTOCOL, SET PROTOCOL, and
DEFINE PROTOCOL command was out of range.
The valid range is 1 to 16.
Repeater port does not exist or is
out of range

Indicates that the parameter entered with the SET
PORT command was not a valid port number. Use the
SHOW REPEATER command to determine which hub
slots contain repeaters and to determine the number
of ports on each repeater.

Station address number
[first [,last] ] in range 1-200

Indicates that one or more parameters entered with
the SHOW PROTOCOL command was out of range.
The valid range is 1 to 200.
(continued on next page)

4–22 Managing the DECbridge 90

Table 4–4 (Cont.) DECbridge 90 Error Messages
Error Message

Description

Unsupported by this hardware
revision

This occurs when you attempt to execute a SET or
DEFINE BRIDGE FLOOD command on a bridge with
a firmware revision of 1 (DECbridge 90 V1.4) but have
loaded V2.5 flash EPROM. The old hardware revision
does not support flood mode. These version numbers
appear in the MOP console connection banner.

???

Indicates that a command or parameter was not
recognized. Type ? to display valid commands.

180501

Appears whenever a loopback diagnostic is run and
passed on the backbone port. If the backbone port
is not receiving any messages, this diagnostic is run
every 10 minutes.

180201

Appears whenever a loopback diagnostic is run and
passed on the work group port. If the work group port
is not receiving any messages, this diagnostic is run
every 10 minutes.

1805:00-00-00-00
01

Appears whenever a loopback diagnostic is run and
fails on the backbone port. The diagnostic is tried
every five seconds until the test passes.

1802:00-00-00-00
01

Appears whenever a loopback diagnostic is run and
fails on the work group port. The diagnostic is tried
every five seconds until the test passes.

Managing the DECbridge 90 4–23

5
Troubleshooting
This chapter describes how to troubleshoot the DECbridge 90 unit. The indicators
on the front panel of the DECbridge 90 are used to troubleshoot bridge and work
group problems. Figure 1–2 in Chapter 1 shows the location of the indicator
lights and connectors on the DECbridge 90. To troubleshoot a unit, follow this
procedure:
1. Verify the installation of the bridge.
Ensure that the installation meets the configuration requirements provided in
Chapter 2.
2. Check all power and Ethernet connections.
3. Isolate the problem. When isolating a problem, examine the following:
•

Backbone

•

Connection to the backbone

•

Work group

•

Connection to the work group

•

DECbridge 90

•

Power supply

Troubleshooting 5–1

Table 5–1 lists the state of the LEDs, the possible causes, and the corrective
action.
Table 5–1 Activity Indicators (LEDs)
LED

State

Possible Cause

Corrective Action

DC OK

Bridge’s power supply is
working.

None.

OFF

Bridge’s power supply is not
working or there are transceiver
problems.

Go to Table 5-2.

Must be in slot 7 of hub.
System OK

Bridge is powered up and has
passed the self-test.

None.

OFF

Bridge is faulty.

Go to Table 5-2.

Bridge is powered up and has
passed the self-test.

None.

OFF

Cables are not properly
terminated1 .

Refer to Chapter 2.

Work Group
Port Activity

ON2

Indicates activity on the LAN.

None.

Bridge
Forwarding
State

Bridge is not forwarding.

It is normal for this
LED to remain on for
30 seconds after power
up. However, if the
LED remains on for
longer than 30 seconds,
or if the LED goes on
any time during normal
operation, then ensure
that the configuration
is correct and that
all parts are properly
connected.

OFF

Bridge is forwarding.

None.

Work Group
Port OK

1
ThinWire ports of the DECbridge 90 are not terminated internally. External 50-ohm terminations
are required.
2

Can be on, off, or blinking depending on the amount of network traffic.

(continued on next page)

5–2 Troubleshooting

Table 5–1 (Cont.) Activity Indicators (LEDs)
LED

State

Possible Cause

Corrective Action

Maximum Work
Group Size
Exceeded

More than 200 stations are
connected to the DECbridge 90.3

Review configuration
rules in Chapter 2.

OFF

Work group size is fine.

None.

Backbone port self-test is
completed.

None.

OFF

Cables are not properly
terminated1 or there is a
network fault on the backbone
wires.

Refer to backplane
installation procedures
in Chapter 3.

ON2

There is activity on the LAN.

None.

Backbone Port
OK

Backbone Port
Activity

1
ThinWire ports of the DECbridge 90 are not terminated internally. External 50-ohm terminations
are required.
2

Can be on, off, or blinking depending on the amount of network traffic.

Light remains on for approximately 10 minutes after bridge discovers that the work group no longer
exceeds the 200-station limit.

Troubleshooting 5–3

Table 5–2 lists some possible problems and the suggested corrective action.
Table 5–2 Simple Troubleshooting
Problem

Suggested Corrective Action

All LEDs off; power
is not reaching the
DECbridge 90

Secure the power cable at the bridge and at the wall outlet.
Check the wall outlet using another appliance or light, or plug the
bridge’s power cord into another outlet. If no power is available,
check the wall outlet’s circuit breaker.
Replace a defective bridge power cable with a new cable.
Check for a short circuit in the AUI transceiver cable. Remove
power from the DECbridge 90 and remove the transceiver cable,
and reconnect power to the bridge. If the power light now comes on,
repair the transceiver or transceiver cable.
If the fault persists, more extensive troubleshooting is required.
Notify the system or network manager.

DC OK off, any
other LED on

If AUI cable is attached, check transceiver cable or transceiver for
short circuits.
If connected to the DEChub 90 backplane, make sure that the
DECbridge 90 is in slot 8.
If the problem still exists, notify the system or network manager
that the power supply must be replaced.

Bridge Forwarding
State LED on

Indicator normally remains on for 30 seconds after power up while
bridge learns network configuration, and then the indicator turns
off. If the indicator remains on, be sure both Work Group Port OK
and Backbone Port OK indicators are on. If they are not on, verify
cable terminations.
Check the work group to be sure that there are no redundant paths
into the work group; see the configuration rules in Chapter 2.
(continued on next page)

5–4 Troubleshooting

Table 5–2 (Cont.) Simple Troubleshooting
Problem

Suggested Corrective Action

Station in
backbone cannot
communicate to
station in the work
group

Be sure Bridge Forwarding State LED is off.
Be sure the protocol in use is not being filtered.
The receiving station has never transmitted a message, or has
not transmitted a message in the last 15 minutes. Stations in the
work group must transmit at least one message every 15 minutes
to remain in the DECbridge 90 address table. This is the address
age time, and may be lengthened with management. (All Digital
stations transmit a periodic ID every 8 to 12 minutes.)
If a station never transmits, you may wish to enable flood mode to
allow the station to receive messages from the backbone. Refer to
the Flood Mode section of Chapter 4.

A station in the
work group cannot
communicate to
a station in the
backbone
DECbridge 90 does
not work in the
backplane

Be sure the Bridge Forwarding State LED is off.
Be sure the protocol in use is not being filtered.

Verify that the bridge is installed in slot 8 of the backplane.

Customer Services Option
If you need additional assistance in troubleshooting the DECbridge 90 or if you
need to replace the unit, call your local Digital Services representative or vendor.

Troubleshooting 5–5

A
Specifications and Parts List
This appendix provides the specifications and parts list for the DECbridge 90
unit.
Specifications for the DECbridge 90 are divided into the following categories:
•

Physical dimensions

•

Environmental (operating and shipping) specifications

•

Power specifications

Table A–1 lists the physical dimensions of the DECbridge 90.
Table A–1 Physical Dimensions
Dimension

Value

Height

3.18 cm (1.25 in)

Width

27.31 cm (10.75 in)

Depth

14.61 cm (5.75 in)

Weight

.45 kg (1 lb)

Table A–2 lists the operating environment specifications for the DECbridge 90.

Specifications and Parts List A–1

Table A–2 Operating Environment
Item

Value

Temperature

5°C to 50°C (41°F to 122°F)

Maximum rate of change

20°C/hr (36°F/hr)

Relative humidity

10% to 95% (noncondensing)

Wet-bulb temperature

32°C (90°F) maximum

Dew point

2°C (36°F) minimum

Altitude

Sea level to 2.4 km (8000 ft)

Air flow

Convectively cooled. A minimum of 10 cm (4 in) of space must
be provided on both ends of the unit for adequate air flow.

The DECbridge 90 is designed to operate in an office environment. It cannot be
installed in an air plenum.
Table A–3 lists the shipping environment specifications for the DECbridge 90.
Table A–3 Shipping Environment
Item

Value

Temperature

-40°C to 66°C (-40°F to 151°F)

Relative humidity

10% to 95% (noncondensing)

Altitude

Sea level to 4.9 km (16,000 ft)

Table A–4 lists the power specifications for the DECbridge 90.
Table A–4 Power Specifications
Item

Value

Voltage (Domestic)

104 Vac to 128 Vac (nominal 120 Vac)

Voltage (International)

208 Vac to 256 Vac (nominal 240 Vac)

Current at 120 V

.77 A

Current at 240 V

.77 A

Frequency

50 Hz to 60 Hz

Power consumption

5.68 W

A–2 Specifications and Parts List

Parts List
Table A–5 lists the kit contents for a standalone installation.
Table A–5 Standalone Installation Kit Contents
Part

Order Number

DECbridge 90 kit:

DEWGB-AA

•

Power supply with 2.4 m (8 ft) dc cable
attached (H7827-AA)

•

AC power cord

•

DECbridge 90 (DEWGB-MA)

•

Owner’s manual (EK-DEWGB-OM)

Table A–6 lists the kit contents for the installation in a DEChub 90 backplane.
Table A–6 DEChub 90 Backplane Installation Kit Contents
Part

Order Number

DECbridge 90 kit:

DEWGB-MA

•

DECbridge 90

•

Owner’s manual (EK-DEWGB-OM)

Specifications and Parts List A–3

B
Related Documentation
This appendix lists related documentation and provides ordering information.
Document Title

Order Number

Bridge and Extended LAN Reference

EK-DEBAM-HR

DECconnect System Facilities Cabling
Installation Guide

EK-DECSY-FC

DECconnect System Planning and Configuration
Guide

EK-DECSY-CG

DEChub 90 Owner’s Manual

EK-DEHUB-OM

Network Troubleshooting Guide

EK-339AA-GD

Networks and Communications Product
Documentation

EK-NACPD-RE

Remote Bridge Management Software Guide

AA-FY93C-TE

Ordering Information
Customers may order documents by phone or mail.

Continental USA and Puerto Rico
Call 1-800-258-1710 or send mail to:
Digital Equipment Corporation
Peripherals and Supplies Group
P.O. Box CS2008
Nashua, NH 03061