Cabletron Systems SEHI-22 User manual

SEHI-22 AND SEHI-24 10BASE-T
INTELLIGENT STACKABLE HUBS
USER’S GUIDE
CABLETRON SYSTEMS, P. O. Box 5005, Rochester, NH 03866-5005

SEHI USER’S GUIDE i
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 August 1995 by: Cabletron Systems, Inc., P.O. Box 5005, Rochester, NH 03866-5005
All Rights Reserved
Printed in the United States of America
Order Number: 9031490 August 1995
SPECTRUM , LANVIEW , and RemoteLANVIEW are registered trademarks and EPIM , EPIM-A ,
EPIM-F1 , EPIM-F2 , EPIM-F3 , EPIM-T , EPIM-X , FOT-F , FOT-F3 , HubSTACK ,
MicroMMAC , SEH , SEHI , and TMS-3 are trademarks of Cabletron Systems, Inc.
i960 is a registered trademark of Intel Corporation.
CHAMP is a trademark of AMP, Inc.
CompuServe is a registered trademark of CompuServe, Inc.
DEC , VT200 , VT300 , and VT320 are trademarks of Digital Equipment Corporation.
Ethernet is a trademark of Xerox Corporation.
IBM is a registered trademark of International Business Machines Corporation.
ST is a registered trademark of American Telephone and Telegraph Company.
UNIX is a trademark of Unix Systems Laboratories, Inc.
Windows is a registered trademark of Microsoft Corporation.
This electric hazard symbol appears in the SEHI User’s Guide. Read all
instructions following this symbol. Failure to follow the instructions
appearing with this symbol could result in the presence of an electric
hazard which has the potential to cause injury.
Printed On Recycled Paper

NOTICE
ii SEHI USER’S GUIDE
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.
NOTE: This equipment has been tested and found to comply with the limits for a Class A digital
device,pursuanttoPart15of the FCC rules.These limits are designedto provide reasonable protection
against harmful interference when the equipment is operated in a commercial environment. This
equipment uses, generates, and can radiate radio frequency energy and if not installed in accordance
with the operator’s manual, may cause harmful interference to radio communications. Operation of
thisequipment in a residentialarea is likelyto cause interference inwhich case theuserwill be required
to correct the interference at his own expense.
WARNING: Changes or modifications made to this device which are not expressly approved by the
party responsible for compliance could void the user’s authority to operate the equipment.
DOC NOTICE
This digital apparatus does not exceed the Class A limits for radio noise emissions from digital
apparatus set out in the Radio Interference Regulations of the Canadian Department of
Communications.
Le présent appareil numérique n’émet pas de bruits radioélectriques dépassant les limites applicables
aux appareils numériques de la class A prescrites dans le Règlement sur le brouillage radioélectrique
édicté par le ministère des Communications du Canada.
VCCI NOTICE
This equipment is in the 1st Class Category (information equipment to be used in commercial and/or
industrial areas) and conforms to the standards set by the Voluntary Control Council for Interference
by Information Technology Equipment (VCCI) aimed at preventing radio interference in commercial
and/or industrial areas.
Consequently, when used in a residential area or in an adjacent area thereto, radio interference may be
caused to radios and TV receivers, etc.
Read the instructions for correct handling.

NOTICE
SEHI USER’S GUIDE iii
CABLETRON SYSTEMS, INC.
PROGRAM LICENSE AGREEMENT
IMPORTANT: Before utilizing this product, carefully read this License Agreement.
This document is an agreement between you, the end user, and Cabletron Systems, Inc. (“Cabletron”)
that sets forth your rights and obligations with respect to the Cabletron software program (the
“Program”) contained in this package. The Program may be contained in firmware, chips or other
media. BY UTILIZING THE ENCLOSED PRODUCT, YOU ARE AGREEING TO BECOME
BOUND BY THE TERMS OF THIS AGREEMENT, WHICH INCLUDES THE LICENSE AND
THE LIMITATION OF WARRANTY AND DISCLAIMER OF LIABILITY. IF YOU DO NOT
AGREE TO THE TERMS OF THIS AGREEMENT, PROMPTLY RETURN THE UNUSED
PRODUCT TO THE PLACE OF PURCHASE FOR A FULL REFUND.
CABLETRON SOFTWARE PROGRAM LICENSE
1. LICENSE. You have the right to use only the one (1) copy of the Program provided in this
package subject to the terms and conditions of this License Agreement.
You may not copy, reproduce or transmit any part of the Program except as permitted by the
Copyright Act of the United States or as authorized in writing by Cabletron.
2. OTHER RESTRICTIONS. You may not reverse engineer, decompile, or disassemble the
Program.
3. APPLICABLE LAW. This License Agreement shall be interpreted and governed under the
laws and in the state and federal courts of New Hampshire. You accept the personal jurisdiction
and venue of the New Hampshire courts.

NOTICE
iv SEHI USER’S GUIDE
EXCLUSION OF WARRANTY
AND DISCLAIMER OF LIABILITY
1. EXCLUSION OF WARRANTY. Except as may be specifically provided by Cabletron in
writing, Cabletron makes no warranty, expressed or implied, concerning the Program (including
its documentation and media).
CABLETRON DISCLAIMS ALL WARRANTIES, OTHER THAN THOSE SUPPLIED TO
YOU BY CABLETRON IN WRITING, EITHER EXPRESSED OR IMPLIED, INCLUDING
BUT NOT LIMITED TO IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR A PARTICULAR PURPOSE, WITH RESPECT TO THE PROGRAM, THE
ACCOMPANYING WRITTEN MATERIALS, AND ANY ACCOMPANYING
HARDWARE.
2. NO LIABILITY FOR CONSEQUENTIAL DAMAGES. IN NO EVENT SHALL
CABLETRON OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER
(INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF BUSINESS,
PROFITS, BUSINESS INTERRUPTION, LOSS OF BUSINESS INFORMATION, SPECIAL,
INCIDENTAL, CONSEQUENTIAL, OR RELIANCE DAMAGES, OR OTHER LOSS)
ARISING OUT OF THE USE OR INABILITY TO USE THIS CABLETRON PRODUCT,
EVEN IF CABLETRON HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
DAMAGES. BECAUSE SOME STATES DO NOT ALLOW THE EXCLUSION OR
LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES, OR
ON THE DURATION OR LIMITATION OF IMPLIED WARRANTIES, IN SOME
INSTANCES THE ABOVE LIMITATIONS AND EXCLUSIONS MAY NOT APPLY TO
YOU.
UNITED STATES GOVERNMENT
RESTRICTED RIGHTS
The enclosed product (a) was developed solely at private expense; (b) contains “restricted computer
software” submitted with restricted rights in accordance with Section 52227-19 (a) through (d) of the
Commercial Computer Software - Restricted Rights Clause and its successors, and (c) in all respects
is proprietary data belonging to Cabletron and/or its suppliers.
For Department of Defense units, the product is licensed with “Restricted Rights” as defined in the
DoD Supplement to the Federal Acquisition Regulations, Section 52.227-7013 (c) (1) (ii) and its
successors, and use, duplication, disclosure by the Government is subject to restrictions as set forth in
subparagraph (c) (1) (ii) of the Rights in Technical Data and Computer Software clause at 252.227-
7013. Cabletron Systems, Inc., 35 Industrial Way, Rochester, New Hampshire 03867.

SEHI USER’S GUIDE v
TABLE OF CONTENTS
CHAPTER 1 INTRODUCTION
1.1 USING THIS MANUAL............................................................................1-1
1.2 GETTING HELP ......................................................................................1-2
1.3 SEHI OVERVIEW....................................................................................1-3
1.4 SEHI FEATURES....................................................................................1-3
1.5 STACKABLE CAPABILITIES ..................................................................1-4
1.6 REMOTE NETWORK MANAGEMENT CAPABILITIES..........................1-5
1.7 OPTIONAL FEATURES ..........................................................................1-5
1.8 RELATED MANUALS..............................................................................1-7
CHAPTER 2 INSTALLATION
REQUIREMENTS/SPECIFICATIONS
2.1 CABLE SPECIFICATIONS......................................................................2-1
2.1.1 HubSTACK Interconnect Cable Requirements........................ 2-1
2.1.2 UTP and STP Cable Specifications.......................................... 2-2
2.2 NETWORK PORT SPECIFICATIONS ....................................................2-4
2.3 COM PORT REQUIREMENTS ...............................................................2-4
2.4 TRANSCEIVER REQUIREMENTS.........................................................2-5
2.5 OPERATING SPECIFICATIONS.............................................................2-5
CHAPTER 3 INSTALLATION
3.1 UNPACKING THE SEHI..........................................................................3-1
3.2 PRE-INSTALLATION CHECKOUT .........................................................3-2
3.3 INSTALLING THE SEHI..........................................................................3-2
3.3.1 Tabletop or Shelf Installation.................................................... 3-3
3.3.2 Rackmount Installation Requirements...................................... 3-4
3.3.3 Attaching the Strain Relief Bracket........................................... 3-5
3.3.4 Rackmounting the SEHI........................................................... 3-6
3.3.5 Stacking the SEHI.................................................................... 3-7
3.4 CONNECTING THE SEHI TO THE POWER SOURCE..........................3-9
3.5 ADDING/REPLACING EPIMs ...............................................................3-10
CHAPTER 4 CONNECTING TO THE NETWORK
4.1 CONNECTING THE SEHI TO THE NETWORK .....................................4-1
4.1.1 Connecting to Network Ports, SEHI-22 and SEHI-24 .............. 4-1
4.1.2 Connecting a UTP Segment to an EPIM-T .............................. 4-3
4.1.3 Connecting a Fiber Segment to an EPIM-F1/F2/F3................. 4-4
4.1.4 Connecting a Thin-Net Segment to an EPIM-C ....................... 4-7
4.1.5 Connecting an AUI Cable to an EPIM-A .................................. 4-8
4.1.6 Connecting an AUI Cable to an EPIM-X ................................ 4-10
4.2 FINISHING THE INSTALLATION..........................................................4-11

CONTENTS
vi SEHI USER’S GUIDE
CHAPTER 5 TROUBLESHOOTING
5.1 INSTALLATION CHECK-OUT.................................................................5-1
5.2 USING LANVIEW ....................................................................................5-2
5.3 USING THE RESET BUTTON.................................................................5-4
5.4 SETTING THE NVRAM SWITCH............................................................5-5
CHAPTER 6 LOCAL MANAGEMENT
6.1 MANAGEMENT TERMINAL REQUIREMENTS......................................6-2
6.1.1 Console Cable Configuration.................................................... 6-2
6.1.2 Management Terminal Setup Parameters................................ 6-3
6.2 ACCESSING LOCAL MANAGEMENT....................................................6-5
6.3 USING THE LOCAL MANAGEMENT SCREENS ...................................6-7
6.3.1 The Community Name Table Screen....................................... 6-7
6.3.2 The Configuration Screen....................................................... 6-10
6.3.3 The Trap Table Screen........................................................... 6-15
6.3.4 The SNMP Tools Screen........................................................ 6-17
6.3.5 The Device Statistics Screen.................................................. 6-22
APPENDIX A EPIM INFORMATION
A.1 EPIM SPECIFICATIONS........................................................................ A-1
A.1.1 EPIM-T ..................................................................................... A-1
A.1.2 EPIM-F1 and EPIM-F2............................................................. A-2
A.1.3 EPIM-F3 ................................................................................... A-3
A.1.4 EPIM-C..................................................................................... A-5
A.1.5 EPIM-A and EPIM-X (AUI Port)................................................ A-6
APPENDIX B IMAGE FILE DOWNLOAD USING OIDs
B.1 SETTING UP A UNIX WORKSTATION AS A TFTP SERVER............... B-1
B.2 STANDARD LOCAL DOWNLOAD......................................................... B-3
INDEX

SEHI USER’S GUIDE 1-1
CHAPTER 1
INTRODUCTION
Welcome to the Cabletron Systems SEHI-22 and SEHI-24 10BASE-T
Intelligent Stackable Hub User’s Guide
. This manual provides
installation instructions and reference information for the SEHI-22 and
SEHI-24.
Figure 1-1. Front and Rear Views of the SEHI-22 and SEHI-24
1.1 USING THIS MANUAL
Read through this manual to gain an understanding of the features and
capabilities of the SEHI. A general knowledge of Ethernet and IEEE
802.3 type data communications networks and their physical layer
components is helpful when installing the SEHI.
HubSTACK10BASE-T HUB WITH LANVIEW®
SEHI-22
1491_1
EPIM-1
EPIM-2
HubSTACK10BASE-T HUB WITH LANVIEW®
SEHI-24
HubSTACK10BASE-T HUB WITH LANVIEW®
SEHI-24
EPIM-1
HubSTACK10BASE-T HUB WITH LANVIEW®
SEHI-22
SEH INTERCONNECT OUT
SEH INTERCONNECT OUT
PWR
CPU
CLN E1
E2
RCV
LNK
RCV
LNK
24 22 20 18 16 14 12 246810
23 21 19 17 15 13 11 13579
2X4X6X8X10X12X
14X16X18X20X22X24X
1X3X5X7X9X11X13X15X17X19X21X23X
COM
RESET
PWR
CPU
CLN E1
RCV
LNK
RCV
LNK
12 246810
11 13579
2X4X6X8X10X12X
1X3X5X7X9X11X
COM
RESET

CHAPTER 1: INTRODUCTION
1-2 SEHI USER’S GUIDE
Chapter 1, Introduction , outlines the contents of this manual, briefly
describes SEHI features, and concludes with a list of related manuals.
Chapter 2,
Installation Requirements/Specifications , describes
installation requirements, network guidelines, and SEHI operating
specifications.
Chapter 3,
Installation , contains instructions for installing the SEHI as a
stackable or stand-alone hub.
Chapter 4,
Connecting to the Network , explains how to connect the
SEHI to the network using the various media types.
Chapter 5,
Troubleshooting , describes how to use the LANVIEW LEDs
to troubleshoot network problems.
Chapter 6,
Local Management , describes how to use SEHI Local
Management screens and the available commands.
Appendix A,
EPIM Information , provides specifications, cabling
information, and switch settings for the Ethernet Port Interface Modules.
Appendix B,
Image File Download Using OIDs , provides instructions
for setting up a tftp server and downloading image files to the SEHI by
setting specific MIB OID strings.
1.2 GETTING HELP
To obtain additional support related to the Cabletron Systems SEHI, or if
there are any questions, comments, or suggestions concerning this
manual, contact Cabletron Systems Technical Support:
By phone ...................[phone]
Monday-Friday; 8am - 8pm Eastern Time
By CompuServe........GO CTRON from any ! prompt
By Internet mail [email protected]
By FTP......................134.141.197.25
Login:
anonymous , Password: your email address

SEHI OVERVIEW
SEHI USER’S GUIDE 1-3
1.3 SEHI OVERVIEW
The 10BASE-T SEHI-22 and SEHI-24 are intelligent repeater hubs. The
SEHI-22 has 12 RJ45 ports and one Ethernet Port Interface Module
(EPIM) port on the front panel for network connections while the
SEHI-24 has 24 RJ45 ports and two EPIM ports on the front panel for
network connections. Both models have one rear panel HubSTACK
Interconnect Bus port for stackable connections. The SEHI is designed to
manage the Cabletron SEH series of non-intelligent stackable hubs.
1.4 SEHI FEATURES
Repeater Functionality
The SEHI fully conforms to the IEEE 802.3 Repeater, AUI, and
10BASE-T specifications, and provides the flexibility to connect
networks using IEEE 802.3, Ethernet Version 1 or Version 2 equipment.
The SEHI transmits retimed data packets, regenerates the preamble,
extends fragments, and arbitrates collisions.
The SEHI automatically partitions problem segments, and reconnects
repaired segments to the network. This feature minimizes the impact on
network operation resulting from a problem on one segment by isolating
the problem segment. Only devices on the problem segment are affected.
When the problem is solved, the SEHI automatically reconnects the
isolated segment to the network.
Polarity Detection and Correction
Each twisted pair port on the SEHI incorporates a Polarity Detection and
Correction feature that allows the SEHI to pass data regardless of the
polarity of the twisted pair segment’s receive link. Cabletron does not
recommend operating in this condition. When this condition is detected,
remove the segment from the network and wire it correctly to reduce the
potential for problems if equipment changes are made.
Flash EEPROMs
The SEHI uses Flash EEPROMs that allow the downloading of new and
updated firmware in conjunction with Cabletron’s Remote LANVIEW/
Windows, version 2.3 or later or any device utilizing BOOTP or TFTP
protocols.

CHAPTER 1: INTRODUCTION
1-4 SEHI USER’S GUIDE
LANVIEW LEDs
Cabletron Systems LANVIEW Status Monitoring and Diagnostics
System is a troubleshooting tool that helps in diagnosing power failures,
collisions, cable faults, and link problems. The LANVIEW LEDs are
conveniently located on the SEHI front panel.
Reset Button
Resetting the hub with the front panel Reset Button reboots the SEHI and
initializes the processor.
Local Management
Manage the SEHI and its attached segments through Local Management
on the SEHI. Local Management provides full packet and error statistics
for the entire stack, individual device, or individual port. Access Local
Management by attaching a DEC VT320 terminal or a PC using VT320
emulation software to the SEHI RJ45 COM port.
1.5 STACKABLE CAPABILITIES
The SEHI intelligent hub is designed to manage the Cabletron series of
SEH non-intelligent hubs. The SEHI serves as the logical “top” of the
stack. It manages all SEH hubs in the stack providing full packet and error
statistics for the entire stack, individual device, or individual port.
Stack up to four SEH non-intelligent hubs with one SEHI using Cabletron
external HubSTACK Interconnect cables. Stackable configurations make
it possible to maintain only one IEEE repeater hop while providing up to
130 Ethernet ports. Hubs can be added or removed from the stack without
having to power down the entire stack.

REMOTE NETWORK MANAGEMENT CAPABILITIES
SEHI USER’S GUIDE 1-5
1.6 REMOTE NETWORK MANAGEMENT CAPABILITIES
Manage the SEHI remotely with any SNMP network management
system. Cabletron Systems offers the following remote management
packages:
• Cabletron Systems SPECTRUM
• Cabletron Systems Remote LANVIEW/Windows
• Cabletron Systems Remote SPECTRUM Portable Management
Applications
• Third Party SNMP compliant Network Management Packages
1.7 OPTIONAL FEATURES
The following features are not included with the SEHI, but can be
purchased separately from Cabletron Systems.
Ethernet Port Interface Modules (EPIMs)
EPIMs enable the expansion of your network through a variety of media.
Cabletron Systems offers the EPIMs shown in Table 1-1.
Table 1-1. EPIMs
EPIM MediaType Connector
EPIM-A AUI DB15 (Female)
EPIM-C 10BASE-2 Thin Coaxial BNC
EPIM-T 10BASE-T Unshielded
Twisted Pair RJ45
EPIM-X Standard Transceiver DB15 (Male)
EPIM-F1 Multimode Fiber SMA
EPIM-F2 Multimode Fiber ST
EPIM-F3 Single Mode Fiber ST

CHAPTER 1: INTRODUCTION
1-6 SEHI USER’S GUIDE
Table 1-2 lists the board revision requirements for EPIMs used in the
SEHI-22/24. The board revision number is located on the EPIM’s printed
circuit board directly after the part number as shown in Figure 1-2.
Figure 1-2. EPIM Board Revision Number
Table 1-2. EPIM Board Revision Requirements
EPIM EPIM Board Revision
EPIM-A Not Applicable
EPIM-C 05 or greater
EPIM-T 04 or greater
EPIM-X 02 or greater
EPIM-F1 05 or greater
EPIM-F2 05 or greater
EPIM-F3 02 or greater
CABLETRON SYSTEMS INC. PN 9000474 - 04
EPIM Board Revision
EPIM-T
1490_2

RELATED MANUALS
SEHI USER’S GUIDE 1-7
HubSTACK Interconnect Cables
Stack hubs together with Cabletron HubSTACK Interconnect cables.
Table 1-3 lists the part number and the application for each cable.
Rack Mount Capabilities
The SEHI can be installed in a 19-inch rack. Cabletron offers an
accessory package that includes the brackets, a strain relief for cable
management and mounting screws. The part number for the accessory
package is SEHI-ACCY-KIT. See Chapter 3,
Installation , for complete
rack mounting instructions.
Local Management Console Cable
An RJ45 console cable is used to attach the SEHI to a management
terminal. The console cable is not included with the SEHI but is included
in the same accessory package as the rackmount kit listed above. The part
number for the accessory kit is SEHI-ACCY-KIT. See Chapter 6,
Local
Management
, for details on setting up, accessing and managing the
SEHI through local management.
1.8 RELATED MANUALS
Use the Cabletron Systems SEH-22 and SEH-24 10BASE-T User’s
Guide
to supplement the procedures and other technical data provided in
this manual. The procedures contained in the
SEH-22 and SEH-24
10BASE-T User’s Guide
are referenced where appropriate, but not
repeated in this manual.
Table 1-3. HubSTACK Interconnect Cables
Part
Number Description Application
9380110 12" HubSTACK
Interconnect Cable SEH to SEH connections
9380111 18" HubSTACK
Interconnect Cable SEHI to SEH connections

SEHI USER’S GUIDE 2-1
CHAPTER 2
INSTALLATION
REQUIREMENTS/SPECIFICATIONS
This Chapter describes cabling requirements, network guidelines, and
operating specifications for the SEHI. The network must meet the
requirements and conditions specified in this chapter to obtain satisfactory
performance from this equipment. Failure to follow these guidelines
could result in poor network performance.
2.1 CABLE SPECIFICATIONS
The SEHI-22 and SEHI-24 network ports support Shielded Twisted Pair
(STP) or Unshielded Twisted Pair (UTP) cabling.
Ethernet Port Interface Modules (EPIMs) expand a network using UTP,
STP, Multimode Fiber Optic, Single Mode Fiber Optic, or Thin Coaxial
cabling. For information concerning EPIMs, refer toAppendix A. The
rear panel Interconnect Bus port supports Cabletron Systems HubSTACK
Interconnect cables for stackable applications.
Take care in planning and preparing the network cabling and connections.
The quality of the connections and the length of cables are critical factors
in determining the reliability of the network. The following sections
describe specifications for each media type.
2.1.1 HubSTACK Interconnect Cable Requirements
Attach the SEHI to modules in the stack with the SEHI HubSTACK
Interconnect cable available only from Cabletron Systems. Refer to
Chapter 1 for cable part numbers. The cable attaches to the SEHI rear
panel bus port.
The rear panel of the SEHI has an Interconnect Bus Out port (male
connector) to stack SEH non-intelligent hubs together. Stack up to four
SEH hubs together with one SEHI.

CHAPTER 2: INSTALLATION REQUIREMENTS/SPECIFICATIONS
2-2 SEHI USER’S GUIDE
2.1.2 UTP and STP Cable Specifications
The device at the other end of the twisted pair segment must meet IEEE
802.3 10BASE-T specifications. When connecting a 10BASE-T Twisted
Pair Segment to the SEHI 10BASE-T Twisted Pair Network Ports and
EPIM-T module, the network must meet the following requirements:
Length
The IEEE 802.3 10BASE-T standard requires that 10BASE-T devices
transmit over a 100 meter (328 foot) link using 22-24 AWG unshielded
twisted pair wire. However, cable quality largely determines the
maximum link length. With high quality, low attenuation cable, link
lengths of up to 200 meters are achievable. Cable delay limits the
maximum link length to 200 meters, regardless of the cable type.
Insertion Loss
The maximum insertion loss allowed for a 10BASE-T link is 11.5 dB at
all frequencies between 5.0 and 10 MHz. This includes the attenuation of
the cables, connectors, patch panels, and reflection losses due to
impedance mismatches in the link segment.
Impedance
Cabletron Systems 10BASE-T Twisted Pair products work on twisted pair
cable with 75 to 165 ohms impedance. Unshielded twisted pair cables
typically have an impedance of between 85 to 110 ohms.
Shielded twisted pair cables, such as IBMType 1 cable, are also used. The
impedance of IBM Type 1 cable is typically 150 ohms. Higher impedance
IBM Type 1 cable increases signal reflection, but because the cable is
shielded, signal reflection has little effect on the received signal’s quality
due to the lack of crosstalk between the shielded cable pairs.
Jitter
Intersymbol interference and reflections cause jitter in the bit cell timing,
resulting in data errors. A 10BASE-T link must not generate more than
5.0 ns of jitter. If the cable meets the impedance requirements for a
10BASE-T link, jitter should not be a concern.

CABLE SPECIFICATIONS
SEHI USER’S GUIDE 2-3
Delay
The maximum propagation delay of a 10BASE-T link segment must not
exceed 1000 ns. This 1000 ns maximum delay limits the maximum link
segment length to no greater than 200 meters.
Crosstalk
Crosstalk is caused by signal coupling between the different cable pairs
contained within a multi-pair cable bundle. 10BASE-T transceivers are
designed so that the user does not need to be concerned about cable
crosstalk, provided the cable meets all other requirements.
Noise
Noise is caused by either crosstalk or externally induced impulses.
Impulse noise may cause data errors if the impulses occur at very specific
times during data transmission. Generally, the user need not be concerned
about noise. If noise-related data errors are suspected, it may be necessary
to either reroute the cable or eliminate the source of the impulse noise.
Temperature
Multi-pair PVC 24 AWG wires typically have an attenuation of
approximately 8 to 10 dB/100 meters at 20°C (68°F). The attenuation of
PVC insulated cable varies significantly with temperature.
At temperatures greater than 40°C (104°F), Cabletron recommends the
use of plenum-rated cables to ensure that cable attenuation remains within
specification.

CHAPTER 2: INSTALLATION REQUIREMENTS/SPECIFICATIONS
2-4 SEHI USER’S GUIDE
2.2 NETWORK PORT SPECIFICATIONS
The SEHI-22 and SEHI-24 network ports use shielded RJ45 connectors
that support STP and UTP cabling. Figure 2-1 shows the RJ45 pinouts.
Figure 2-1. RJ45 Network Ports
2.3 COM PORT REQUIREMENTS
The RJ45 COM port supports access to a Local Management Console.
The Console port supports a Digital Equipment Corporation, VT320
terminal or PC emulation of the VT320 terminal. Figure 2-2 shows the
pinouts for the RJ45 COM port.
Figure 2-2. COM Port Pinouts
1 2 3 4 5 6 7 8
1. Receive + 5. Not Used
2. Receive - 6. Transmit -
3. Transmit + 7. Not Used
4. Not Used 8. Not Used
5X 3X 1X
1490_3
1. Transmit Data
2. Data Carrier Detect
3. Data Set Ready
4. Receive Data
5. Signal Ground
6. Data Terminal Ready
7. Request To Send
8. Clear To Send
1 2 3 4 5 6 7 8
COM
1490_36

TRANSCEIVER REQUIREMENTS
SEHI USER’S GUIDE 2-5
2.4 TRANSCEIVER REQUIREMENTS
When connecting an external network segment via a transceiver to the
SEHI with an EPIM-A, the following requirements must be met:
• The transceiver or Ethernet Device to which the module will be
connected must meet IEEE 802.3 standards, and/or Ethernet
Version 1.0 or Version 2.0 standards.
• The Signal Quality Error (SQE) test function on the transceiver
must be disabled when it is connected to a repeater or to an
Ethernet Version 1.0 device. In addition, some Version 2.0
equipment does not support the SQE test. Devices that do not
support the SQE test interpret the SQE test pulse as a collision.
2.5 OPERATING SPECIFICATIONS
The operating specifications for the SEHI are described in this section.
Cabletron Systems reserves the right to change these specifications at any
time without notice.
General
Operating System Memory: 1.5 MB
Internal Processor: Intel i960 operating at 16 MHz
Ethernet Controller: National Semiconductor DP83916
Non-Volatile RAM: 32 KB with battery back-up
EPROM: 64 KB
FLASH MEMORY: 1 MB

CHAPTER 2: INSTALLATION REQUIREMENTS/SPECIFICATIONS
2-6 SEHI USER’S GUIDE
Delay Times (Start of Packets):
Twisted Pair to EPIM-A 1.10 µs
Twisted Pair to Twisted Pair 1.00 µs
EPIM-A to Twisted Pair 1.00 µs
Delay Times (JAM):
Twisted Pair to EPIM-A 960 ns
Preamble:
Input: Minimum of 40 bits required
Output: 64 bits minimum
(last 2 bits are 1,1)
JAM Output:
Collisions are propagated through
the network using the JAM signal
of an alternating pattern of 1's and
0's in accordance with 802.3
specifications for a repeater unit.
Fragment Extension:
Packet fragments are extended to a
minimum of 96 bits using the JAM
[1,0].