Cabletron Systems Network Router 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.  
© Copyright May 1990 by:  
Cabletron Systems Inc.  
P.O. Box 6257, E. Rochester, NH 03867-6257  
All Rights Reserved  
Printed in the United States of America  
Order Number: 9030040-02 May 90  
Remote LANVIEW, LANVIEW, NB25E, NB20E, and LAN-MD are  
trademarks of Cabletron Systems Inc.  
i
 
FCC NOTICE  
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  
ii  
 
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  
INSTALLING THE 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  
iii  
 
CONTENTS  
iv  
 
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  
USING THIS 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.  
1-1  
 
INTRODUCTION  
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 NB25E TWO 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 Tree Algorithm 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  
1-2  
 
INTRODUCTION  
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.  
1-3  
 
INTRODUCTION  
NODE A  
NODE C  
LAN 1  
T
T
T
T
LAN 2  
NODE B  
Figure 1-1 Bridging Method  
In this example, when Node A 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 Source Address 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 Source Address 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.  
1-4  
 
INTRODUCTION  
This feature is referred to as Aging Time. Aging Time can be altered  
through Cabletron Systems’ Remote LANVIEW Network Control  
Management for the Cabletron Systems' NB20E and NB25E.  
1.5  
MULTIPLE BRIDGE ENVIRONMENTS  
Both the NB20E and NB25E Two Port Bridges are designed to promote  
maximum network use in multiple bridge environments. A bridge learns  
the bridge topology of its network from bridge protocol data that is  
transmitted onto the network by each bridge. The bridges then apply a  
Spanning Tree Algorithm to select a root bridge and to determine primary  
data paths within potential data loop configurations. A Spanning Tree  
Algorithm, as defined earlier, is a hierarchy (or tree) of priorities that is  
established between bridges. This hierarchy guarantees that primary and  
redundant data paths will be clearly defined at all times, so that the  
network is available to users at all times.  
1.5.1  
The Root Bridge  
One bridge in the network is established as the root bridge. This bridge  
has priority over all other bridges. Each bridge in a Spanning Tree must  
learn which bridge is the root and then determine its own relative priority  
within the network.  
Determining the root bridge begins with the broadcast of Bridge Protocol  
Data Units (BPDUs) across the network. When the bridges go on line,  
each bridge sends out a BPDU which contains its priority field and its  
unique identifier or Ethernet address. Through the broadcast of these  
identifiers across the network, the bridges learn which bridge has the  
highest priority, or lowest identifier. This bridge becomes the root bridge  
for the network. Each bridge then determines its own priority in relation  
to this bridge.  
The network manager can, however, override this process for determining  
the root. Using the root switch, the manager can manually select a  
different bridge to be the root by applying a selectable switch at the  
appropriate bridge. This bridge transmits BPDUs to inform the other  
bridges that it is now the root. With this information, the bridges  
immediately learn their new priority in relation to the new root, and the  
system of priorities is maintained.  
1-5  
 
INTRODUCTION  
1.5.2  
Primary and Redundant Data Paths  
To ensure the integrity of the network, primary data paths through  
designated bridges, and redundant data paths through alternative bridges  
are determined in each LAN or loop configuration in the network. A LAN  
segment’s designated bridge is the bridge in a LAN or loop configuration  
with the lowest cost path of transmission from that LAN segment to the  
root bridge. The lowest cost path can be translated in a general way to  
mean the data transmission path to the root that is most economical.  
The bridges in the network send out BPDUs to the other bridges so that  
they can all learn which is the bridge in the network, or in a potential loop  
configuration, with the lowest cost path to the root. The bridges can then  
determine their own priorities and roles as designated or redundant  
bridges. Redundant bridges are “blocked” from forwarding packets, but  
they continue to receive topology information.  
Figure 1-2 provides a sample illustration of how a potential data loop is  
prevented in a simple multibridge environment. A data loop exists  
NODE A  
T
T
T
T
T
NB20E OR 25E  
BRIDGE 1  
NB20E OR 25E  
BRIDGE 2  
T
NB20E OR 25E  
BRIDGE 3  
NODE B  
Figure 1-2 Multiple Bridging Environments  
1-6  
 
INTRODUCTION  
if all three bridges are on line and Node A sends a packet to Node B. The  
packet will be forwarded through Bridges 1 and 3, and through Bridge 2,  
causing the packet to be circulated many times around the data loop. If  
Bridge 1 has priority over Bridge 2, the Spanning Tree Algorithm will  
place Bridge 2 in blocking, preventing the packet from being forwarded  
through Bridge 2. If Bridge 1 should fail, the Spanning Tree Algorithm  
will be modified automatically so that the packet will be forwarded  
through Bridge 2.  
1.6  
REMOTE LANVIEW  
Both the NB20E and the NB25E can be controlled and managed by  
Cabletron Systems' optional Remote LANVIEW - Network Control  
Management for the Cabletron Systems' Bridges. Remote LANVIEW  
allows you to control and manage multiple NB20Es or NB25Es from a  
single Ethernet Workstation through Cabletron System NCM-DOS™ or  
Remote LANVIEW/Windows™ or an individual NB25E through an  
RS232 port on the bridge.  
Remote LANVIEW provides the necessary management tools so that a  
bridge can operate at its full capacity. 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 monitor: the flow of traffic through a bridge, the status of a  
database, the bridge protocol and port parameters, and the bridge setup.  
The number of frames received at the bridge is recorded as well as a  
breakdown of the progress through the bridge, for example the frames  
discarded inbound or the frames forwarded outbound. A breakdown of  
errors is provided so the network manager can pinpoint potential problem  
areas in a network.  
Bridge protocol and port parameters such as Topology Change,  
Designated Root, and Path Cost are provided, so that the network  
manager can keep track of bridge activity and cost. Certain parameters  
can be altered to accommodate a network's particular requirements.  
Remote LANVIEW provides the network manager with the necessary  
control to operate a bridge effectively. For instance, a network manager  
can alter bridge setup, erase a database, disable or restart a bridge, reset  
counters, or restore default settings.  
1-7  
 
INTRODUCTION  
For further information for refer to the Remote LANVIEW - Network  
Control Management for the Cabletron Systems' NB20E and NB25E  
User's Manual.  
1.7  
RELATED MANUALS  
The manuals listed below should be used to supplement the procedures  
and other technical data provided in this manual. The procedures will be  
referenced where appropriate, but will not be repeated.  
Cabletron Systems' Remote LANVIEW - Network Control  
Management for the Cabletron Systems' NB20E and NB25E User’s  
Manual.  
Cabletron Systems' LAN-MD User’s Manual.  
1-8  
 
CHAPTER 2  
INSTALLATION REQUIREMENTS/  
SPECIFICATIONS  
Before you attempt to install Cabletron Systems' NB20E or NB25E Two  
Port Ethernet Bridge, review the location and hardware requirements  
outlined in this chapter. Also refer to the operating specifications and  
environmental requirements that are listed.  
All conditions, guidelines, specifications and requirements included in  
this chapter must be met to ensure satisfactory performance of the NB20E  
or NB25E. Failure to follow these guidelines will result in unsatisfactory  
network performance.  
2.1  
LOCATION REQUIREMENTS  
Before installing the NB20E or NB25E Two Port Ethernet Bridge, ensure  
that the location for the bridge meets the following requirements:  
The location must have an unrestricted surface area 21 inches (53.34  
cm) wide, and must be at least 18 inches (45.72 cm) deep and 6 inches  
(15.24 cm) high.  
A standard 3 prong power receptacle must be located within 7 feet  
(2.13 m) of the site.  
If a shelving unit is to be used, the unit must be able to support 30  
pounds (13.6 kg) of static weight.  
The temperature of the location must be maintained between 5° and  
40°C. Temperature changes of greater than 10°C per hour must not  
occur.  
2.2  
NETWORK REQUIREMENTS  
When bridging two segments using an NB20E or NB25E Two Port  
Bridge, you must follow the network guidelines listed below:  
The transceivers to which the NB20E or NB25E will be connected  
must meet Ethernet Version 1, Version 2, or IEEE 802.3 standards.  
The AUI cables connecting the NB20E or NB25E to the transceivers  
on the network must be IEEE 802.3 type cables and must not exceed  
50 meters in length.  
2-1  
 
INSTALLATION REQUIREMENTS/ SPECIFICATIONS  
2.3  
OPERATING SPECIFICATIONS  
The operating specifications for Cabletron Systems' NB20E or NB25E  
Two Port Bridge Series are included in this section. Cabletron Systems  
reserves the right to change these specifications at any time without  
notice.  
GENERAL  
Parameter  
NB20E  
NB25E  
Packet Buffer Memory (RAM): 128K  
128K  
Internal Processor:  
Ethernet Controller:  
16MHz  
Intel 80186  
16MHz  
Intel 80186  
two 8390  
Ethernet  
two 8390  
Ethernet  
Controllers  
Controllers  
Scratch Ram:  
PERFORMANCE  
Parameter  
512K  
512K  
NB20E  
NB25E  
Packet Filter Rate  
(max. viewed per second):  
15,000 Packets 28,000 Packets  
8,000 Packets 11,000 Packets  
Packet Forward Rate  
(max. viewed per second):  
Forwarding Latency:  
125 µs Min.  
91 µs Min.  
Source Address Table Size:  
Age Time (User Definable):  
2048 Max.  
8191 Max.  
5 Minutes  
(Default)  
5 Minutes  
(Default)  
2-2  
 
INSTALLATION REQUIREMENTS/ SPECIFICATIONS  
FRONT PANEL INDICATORS  
ON LINE  
When lit, this LED indicates the two port  
bridge is on line and operational (green  
indicator).  
STAND BY  
When lit, this LED indicates the bridge is not  
forwarding packets (yellow indicator).  
NOTE: There is one TRANSMIT, RECEIVE, COLLISION, and POK  
(Port OK) LED for each segment. The LEDs for RECEIVE, TRANSMIT  
and COLLISION are pulsed-stretched for increased viewing effect.  
XMT (transmit)  
RCV (receive)  
When lit, this LED indicates the bridge is  
transmitting packets to that segment (green  
indictor).  
When lit, this LED indicates that the bridge  
is receiving data packets from that segment  
(yellow indicator).  
CP (collision present)  
POK (port ok)  
When lit, this LED indicates that a collision  
is occurring on that segment (red indicator).  
When lit, this LED indicates transceiver  
connected, port has passed Loop Back Test  
and is ready for transmission (green  
indicator).  
FRONT PANEL SWITCHES  
FORWARD BROADCAST | / O When this switch is on (|), it allows the  
bridge to forward broadcast messages.  
2-3  
 
INSTALLATION REQUIREMENTS/ SPECIFICATIONS  
FRONT PANEL SWITCHES (cont.)  
ROOT | / O  
When the switch is on ( | ), it designates the  
bridge as the root bridge in the network.  
AUI PORT (NB20E/NB25E)  
Interface Connector  
Type:  
15 position D type receptacle.  
Pin 9 Collision -  
10 Transmit -  
Pin 1 Logic Ref.  
2 Collision +  
3 Transmit +  
4 Logic Ref.  
5 Receive +  
11 Logic Ref.  
12 Receive -  
13 Power (+12 Vdc)  
14 Logic Ref.  
6 Power return  
7 No Connection  
8 Logic Ref  
Connector Shell:  
RS232 PORT  
Type:  
15 No Connection  
Protective Ground  
Standard 9 pin RS232 Port  
Pin 6 NU  
Pin 1 DCD  
2 TX  
7 TRS  
3 RX  
8 CTS  
4 DTR  
9 RX Clock  
5 Signal Ground  
2-4  
 
INSTALLATION REQUIREMENTS/ SPECIFICATIONS  
POWER SUPPLY REQUIREMENTS  
Parameter  
Typical  
Value  
Worst  
Case  
120V Input Voltage: 120 V  
Input Current  
90 to 130 V  
NB20E:  
NB25E:  
0.5 Amps  
0.75 Amps  
1.0 Amps  
1.5 Amps  
Frequency Range:  
47 - 63 Hz  
220V Input Voltage: 220 V  
Input Current  
180 to 264 V  
NB20E:  
NB25E:  
0.25 Amps  
0.375 Amps  
0.5 Amps  
0.75 Amps  
Frequency Range:  
Overload Protection  
Input:  
47 - 63 Hz  
(2) 3AG 3 amp fuses in series with both primary  
inputs.  
Output:  
(2) 3AG 1 amp fuse for each AUI port.  
ENVIRONMENTAL REQUIREMENTS  
Operating Temperature: +5° to +40°C  
Non-operating Temperature: -30° to +90°C  
Operating Humidity: 5 to 95% (non-condensing)  
2-5  
 
INSTALLATION REQUIREMENTS/ SPECIFICATIONS  
SAFETY  
Designed in accordance with UL478, UL910, NEC 725-2(b), CSA, IEC,  
TUV, VDE class A. Meets FCC part 15, Subparagraph J, Class A limits.  
WARNING: It is the responsibility of the person who sells the system of  
which the NB20E or NB25E will be a part to ensure that the total system  
meets allowed limits of conducted and radiated emissions.  
SERVICE  
MTBF (MHBK - 20E):  
NB20E:  
NB25E:  
> 35,750 hrs. projected.  
> 26,533 hrs. projected.  
< 0.5 hrs.  
MTTR:  
PHYSICAL PROPERTIES  
Dimensions:  
3.2H x 17.0W x 12.4D inches  
(8.13 x 38.1 x 31.5 cm)  
Weight  
Unit:  
Shipping:  
7 lbs. (3.17 kg.)  
8 lbs. (3.63 kg.)  
2-6  
 
CHAPTER 3  
INSTALLING THE NB20E OR NB25E BRIDGE  
This section contains instructions for installing Cabletron Systems'  
NB20E or NB25E Two Port Ethernet Bridge, and for preparing the bridge  
for operation. Verify that all network design guidelines and site  
requirements listed in Chapter 2, Installation Requirements/  
Specifications, are met before installing the bridge.  
3.1  
UNPACKING THE NB20E OR NB25E BRIDGE  
Before you install the NB20E or NB25E Bridge, you should visually  
inspect the bridge and check the contents of the accessory package. To  
unpack the bridge and accessory package:  
1. Carefully remove the bridge from the shipping box. Save the shipping  
box and materials in the event the unit has to be reshipped.  
2. Slide the two foam end caps off of the bridge and remove the bridge  
from its protective plastic bag. Set the bridge aside to prevent the unit  
from being damaged.  
3. Remove the plastic bag containing the accessory package and check  
that the bag contains the following items:  
one 8 foot (2.44 m) power cord  
one cable support bracket  
two 8-32 x .375 inch screws  
three 6 (15.24 cm) inch cable ties  
rack mount brackets  
Contact Cabletron Systems' Technical Support immediately if any  
discrepancy in materials exists.  
3.2  
INSTALLING THE BRIDGE  
After you have met all requirements listed in Chapter 2, Installation  
Requirements, complete the installation instructions provided in this  
section.  
3-1  
 
INSTALLING THE NB20E OR NB25E BRIDGE  
3.2.1  
Installing the Rack Mount Brackets  
If the NB20E or NB25E will be rack mounted:  
1. Remove the four screws (5, Fig. 3-1) holding the four rubber feet to  
the bridge. This frees the top plastic housing (1) from the bridge.  
2. Carefully remove the top plastic housing.  
3. Remove the four screws (6) holding the bottom plastic housing (4) to  
the bridge’s chassis.  
1.  
2.  
3.  
4.  
Top Housing  
Screws (4)  
Rack Mount Bracket  
Bottom Plastic Housing  
5. Screws (4)  
6. Screws (4)  
7. Rack Mount Bracket  
Figure 3-1 Rack Mount Brackets Installation  
3-2  
 
INSTALLING THE NB20E OR NB25E BRIDGE  
4. Remove the NB20E or NB25E from the bottom housing.  
5. Remove the four screws (2) that secure the cover to the front of the  
bridge. The screws are located on the left and right sides of the bridge  
(closest to the front side), two per side.  
6. Attach the rack mount brackets (3, 7) using the screws removed in step  
5. The bracket should be flush with the front of the bridge.  
3.2.2  
Cable Support Installation  
To install the cable support:  
1. Remove the four cable support screws (3, Fig. 3-2) from the bridge (1).  
2. Attach the cable support (2) to the rear of the bridge using the screws  
removed in step 1.  
3.2.3  
Connecting The Bridge To The Network  
To connect the bridge to the network:  
1. For each network segment to be connected to the bridge, attach an  
external transceiver (1, 9, Fig. 3-3). Refer to the applicable transceiver  
manual to connect the transceiver.  
1. Bridge (NB25 Shown)  
2. Cable Support  
3. Screws  
Figure 3-2 Cable Support Installation  
3-3  
 
INSTALLING THE NB20E OR NB25E BRIDGE  
1
9
10  
8
2
7
3
4
5
6
1. ST-500 Transceiver  
2. AUI Cable  
3. Bridge  
4. AUI Port 2  
5. AUI Port 1  
6.  
7.  
8.  
9.  
Power Receptacle  
Power Cord  
AUI Cable  
ST-500 Transceiver  
10. RS232 Port (NB25E only)  
Figure 3-3 Installation  
2. Attach an AUI cable (2, 8) no more than 50 meters in length to each of  
the transceivers that you connected to each network segment.  
3. Connect the AUI cable from the transceiver to the AUI port (4, 5)  
located on the back panel of the NB20E or NB25E bridge.  
3.2.4  
Setting The Mode Switches  
Before connecting the bridge to the power supply, set the Forward  
Broadcast and Root switches to the appropriate On (|) or  
Off (O) position as defined below:  
If you want the bridge to pass Broadcast messages between segments,  
set the FORWARD BROADCAST switch (Fig. 3-4) to the On (|)  
position.  
If you want this bridge to receive priority over all other bridges on the  
network, set the ROOT switch (Fig. 3-4) to the On (|) position. Only  
ONE bridge on the network should have the ROOT switch enabled.  
3-4  
 
INSTALLING THE NB20E OR NB25E BRIDGE  
XMT  
ON LINE  
NB-25E  
ETHERNET /IEEE 802.3 BRIDGING UNIT  
WITH REMOTE LANVIEW® AND MANAGEMENT  
RCV  
STAND BY  
FORWARD  
BROADCAST  
1
1
0
0
CP  
ROOT  
POK  
1
PORT  
2
Figure 3-4 Bridge Front Panel  
3.2.5  
Connecting The NB20E or NB25E To The Power  
Source  
When installation of the NB20E/NB25E Bridge is complete and the  
switches have been set, connect the bridge to the power source in the  
following manner:  
1. If you have not already done so, plug the power cord (7, Fig. 3-3) into  
the power receptacle (6) located on the rear panel of the bridge.  
2. Plug the power cord into a wall receptacle.  
3. Turn the power switch, located next to the power receptacle, to the on  
position.  
4. Observe the status of the ON-LINE, STANDBY, PORT 1 OK and  
PORT 2 OK LEDs. These LEDs will flash for approximately 10  
seconds as the bridge performs it's internal diagnostics.  
When the bridge finishes its internal diagnostics, the LEDs should be  
in the following conditions:  
ON LINE LED lit, indicating that the bridge is receiving power.  
PORT 1 OK and PORT 2 OK lit, indicating that the ports have  
passed the internal loopback test and are now ready for  
transmission.  
STANDBY on or off, depending on the bridge's position in the  
Spanning Tree Algorithim.  
3-5  
 
INSTALLING THE NB20E OR NB25E BRIDGE  
The following conditions indicate a problem has been detected with  
the bridge:  
The ON-LINE, STANDBY, PORT 1 OK and PORT 2 OK LEDs  
do not start to flash on power up, indicating that the Real Time  
Clock has failed.  
The ON-LINE, STANDBY, PORT 1 OK and PORT 2 OK LEDs  
do not stop flashing after power up, indicating that the Network  
Interface Chip has not been properly initialized.  
A PORT OK LED is not lit, indicating that the port failed the  
loopback test and that the Network Interface Chip for that port  
failed.  
If any of these conditions exist, contact Cabletron Systems Technical  
Support.  
When power connection is complete, use the cable ties that are provided  
to strain-relief all cables to the cable support (2, Fig. 3-2) to relieve  
unnecessary pressure at cable connection points.  
The NB20E or NB25E Bridge is now ready for operation. Before  
transmitting data, test the installation. For this procedure, refer to the  
section, Chapter 4, Testing and LANVIEW.  
3-6  
 
CHAPTER 4  
TESTING AND LANVIEW  
This section contains procedures to test the NB20E or NB25E Two Port  
Ethernet Bridge after it has been connected to the network. A description  
of the LANVIEW LEDs, the Forward Broadcast, and the Root Switch, is  
also provided.  
4.1  
INSTALLATION CHECK-OUT  
After the NB20E or NB25E is connected to the network, verify that  
packets can be passed between the two Ethernet network segments via the  
bridge. Two Ethernet node testers, such as Cabletron Systems'  
LAN-MD™, are required for this procedure to generate valid data  
packets.  
Before you begin, test each Ethernet segment connected to the NB20E or  
NB25E to ensure that the segments meet IEEE 802.3 specification limits.  
1. Move the Forward Broadcast switch on the front panel of the Bridge  
(Fig. 4-1) to the On (|) position. This will allow broadcast messages  
sent by the LAN-MDs to pass through the bridge.  
2. Using a transceiver (1, Fig. 4-2) and an AUI cable, connect a  
LAN-MD (2) to one of the segments connected to the bridge (3).  
3. Select and run test 6 - SERVER on this LAN-MD.  
4. Verify that the Test Status PASS LED is lit and that the Status Code  
reads 000 or 001. If these two conditions are met, the LAN-MD is now  
the SERVER unit and will act as a packet echoer when used with  
another LAN-MD.  
XMT  
ON LINE  
NB-25E  
ETHERNET /IEEE 802.3 BRIDGING UNIT  
RCV  
STAND BY  
WITH REMOTE LANVIEW® AND MANAGEMENT  
FORWARD  
BROADCAST  
1
1
0
0
CP  
ROOT  
POK  
1
PORT  
2
Figure 4-1 LANVIEW LEDs  
4-1  
 
TESTING AND LANVIEW  
5. Using a transceiver (5) and an AUI cable, connect another LAN-MD  
(4) to the other segment connected to the bridge.  
6. Select and run test 4 - NODE on the LAN-MD connected in the  
previous step.  
7. Verify that this test passes. At least 100 packets should be sent and  
received by the bridge, with no errors. Packets will be sent from this  
LAN-MD to the other LAN-MD, acting as the Server, then echoed  
back.  
When the NB20E or NB25E have successfully completed these tests, the  
bridge is ready for normal operation. If any failures were noted, please  
contact Cabletron Systems' Technical Support.  
4.2  
USING LANVIEW  
The NB20E and NB25E Two Port Ethernet Bridges use Cabletron  
Systems' built-in visual diagnostic and status monitoring system called  
LANVIEW. With LANVIEW, network troubleshooting personnel can  
quickly scan LANVIEW's LEDs to observe network status, or diagnose  
network problems. Figure 4-1 displays the LANVIEW LEDs on the  
NB20E and NB25E.  
Seg. A  
Seg. B  
1
5
3
1. ST-500  
2. LAN-MD  
4
2
3. NB 20E/25E  
4. LAN-MD  
5. ST-500 Transceiver  
Figure 4-2 Check Out Configuration  
4-2  
 
TESTING AND LANVIEW  
ON LINE LED  
When this green LED is lit, the bridge is on line and operational. The unit  
has completed a self diagnostics test and is capable of forwarding packets.  
STAND BY LED  
When this yellow LED is lit, the bridge is in the “Stand by” mode and not  
capable of forwarding packets.  
NOTE: There are separate XMT, RCV, CP, and POK LEDs for each port  
on the NB20E and NB25E.  
TRANSMIT (XMT) LED  
When this green LED is flashing, the bridge is transmitting packets to that  
network segment.  
RECEIVE (RCV) LED  
When this yellow LED is flashing, bridge is receiving a data packet from  
that segment.  
COLLISION PRESENT (CP) LED  
When this red LED is flashing, a collision is occurring on that segment.  
PORT OK (POK) LED  
This green LED is lit to indicate that the transceiver is connected, and that  
the port has passed an internal Loop Back Test and is ready for  
transmission.  
4.3  
USING THE FORWARD BROADCAST SWITCH  
The Forward Broadcast switch, Figure 4-1, allows the user to select  
whether the bridge will forward broadcast messages from one network  
segment to the other. When the switch is in the On (|) position, the bridge  
will allow broadcast messages to pass.  
4-3  
 
TESTING AND LANVIEW  
4.4  
USING THE ROOT SWITCH  
In a multiple-bridge environment, the Root switch, Figure 4-1, for a  
particular bridge allows the user to set that bridge as the root bridge. Only  
one bridge can serve as the root bridge in a multiple bridge environment,  
however. In the event that two bridges have been selected as root bridges,  
the bridge in the environment with the lowest identifier will become the  
root bridge.  
4-4  
 

Belkin Switch F1DB102P2 B User Manual
Black Decker Food Saver VS250 Series, VS350 Series, VS450 Series User Manual
Bosch Power Tools Saw 1657 User Manual
Bretford Indoor Furnishings lap18eulba User Manual
Breville Blender BBL420 User Manual
Broan Range QS336SS User Manual
Cadillac GPS Receiver SRX User Manual
Campbell Hausfeld Pressure Washer IN470300AV User Manual
Celestron Telescope StarSeeker User Manual
Chief Manufacturing Crib Toy MSP CM6HABV71 83 User Manual