3Com 3C250B-TX - SuperStack II Hub 100 User manual

100BASE-T4 and 100BASE-TX
Fast Ethernet solution for UTP cabling
100BASE-T Fast Ethernet Cabling
Standards Overview
100BASE-T Fast Ethernet is an IEEE
802.3 international standard for Ethernet
at 100Mbps. Fast Ethernet utilizes the
same protocol (CSMA/CD Media Access
Control) as standard 10BASE-T Ethernet.
This high speed performance along with
3 cable type specifications (100BASE-TX,
100BASE-T4, 100BASE-FX) allow
100Mbps connections across most
types of network cabling
100BASE -T4 (see diagram)
The 100BASE-T4 specification defines
100Mbps Ethernet transmission across
Category 3, Category 4, or Category 5
UTP cable at distances up to 100 meters.
100BASE-T4 uses 4 pairs (8 wires) in
the wire bundle.
100BASE-TX (see diagram)
The 100BASE-TX specification defines
100Mbps Ethernet transmission across
Category 5 UTP cable and Type 1 STP
cable at distances up to 100 meters.
100BASE-TX uses 2 pairs (4 wires) in the
wire bundle. Most 100BASE-TX products
support category 5 UTP cabling only.
100BASE-FX (see diagram)
The 100BASE-FX specification defines
100Mbps Ethernet transmission across
62.5/125 micron multimode fiber at
distances up to 412 meters (distances up
to 2 K supported with full duplex 100BASE-
FX). 100BASE-FX uses 2 strands of multi-
mode fiber.
Introduction
As the use of high performance PCs and
servers and high-bandwidth applications
increases, the use of high throughput
networking grows. The most popular method
for high performance PC and server
connections is 100BASE-T Fast Ethernet.
Fast Ethernet provides a high performance
solution at a low cost and simple integration
with 10BASE-T Ethernet.
With broad usage of Fast Ethernet products
has come the need to support a broader
range of network cabling types. Many
buildings contain unshielded twisted pair
(UTP) wiring which was installed many
years ago. While the majority of desktop PC
connections are made with Category 5 UTP
(data grade UTP) cabling, many connections
are made with Category 3 or Category 4
UTP (voice-grade UTP) cabling.
3Com now provides a complete set of
products which support 100Mbps Fast
Ethernet on Category 3, Category 4, or
Category 5 UTP cable.
Applications
CSMA/CD MAC
Management
MII Interface
Customer Choice
Fiber
(100BASE-FX)
Four-Pair
Category 3,4, 5 UTP
(100BASE-T4)
Two-Pair
Category 5 UTP, 
STP (100BASE-TX)
Fast Ethernet Physical Layer (PHY) Options

Category 3/Category 4/Category 5 UTP Cable Comparison
Category 5 UTP cable is the most common type of UTP cable in use today for data communications, such as for
10BASE-T Ethernet. Many installations, however, have some or all desktop PCs connected using Category 3 or
Category 4 UTP. The chart below compares these common cable types:
Cable Type Manufac. Specs Common Prod.# E-net/Fast E-net Distance E-net/F-enet spec.
Cat. 3 UTP up to 20 MHz AT&T 1010/20100 100 meters 10BASE-T(2 pairs)
AT&T 2001c/2001d 100BASE-T4(4 pairs)
Cat. 4 UTP up to 33 MHz AT&T 1261/2261 100 meters 10BASE-T(2 pairs)
AT&T 2014a 100BASE-T4(4 pairs)
Cat. 5 UTP up to 100 MHz AT&T 1061 100 meters 10BASE-T(2 pairs)
AT&T 2061 100BASE-TX(2 pairs)
100BASE-T4(4 pairs)
100BASE-T4 Connector Pin Out
100BASE-T4 utilizes 4 pairs of wire in a Category
3, 4 or 5 UTP bundle. 100BASE-T4 connections
from a hub to a PC are normally straight-through
100BASE-T4 Recommended Usage
Specification Comparison:
Specification Advantages Disadvantages Recommended Usage
100BASE-T4 -Category 3,4 UTP support -No support for full duplex -Cat. 3 or 4 UTP PC or server connections
-Reliable in unknown UTP -Requires 4 pairs in wire bundle -Mixed category 3/4/5 UTP environment
environment -Cat. 5 envir. w/ components of unknown quality
100BASE-TX -Most common equipment type -No support for cat. 3 or 4 UTP -Cat. 5 UTP PC or server connections
-Support for full duplex -Requires all components be -Any connection which may use full duplex
Cat. 5 certified Fast Ethernet
100BASE-FX -Longer distances -Expensive -Any fiber connection
-Fiber support -Not common for PC or server -Long distance connections
connections
Transmit (1 & 2)
Receive (3 & 6)
Bidirectional (7 & 8)
Desktop Hub
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
100BASE-T4 Cable Pinout
Note: Like 10BASE-T, 100BASE-T transmit/receive crossover 
is in the hub. RJ-45 connectors are shown here.
Bidirectional (4 & 5)
Bidirectional (4 & 5)
SuperStack II Hub 100-TX
Fast Ethernet
SuperStack II Hub 100-T4
Fast Ethernet
Local server with 
Fast EtherLink 
10/100BASE-TX 
NIC
EtherLink III 
10BASE-T NIC
Fast EtherLink 
10/100BASE-TX 
NIC
Fast EtherLink 
10/100BASE-T4 
NIC
Local server
Cat. 3 UTP
Cat. 5 UTP
Central servers with 
10/100BASE-TX 
NICs
SUPERSTACK II
SWITCH 3000
Floor 4
Floor 3
Floor 2
Floor 1
Fast Ethernet switch

Legend
 10 Mbps UTP
 100 Mbps UTP
 100 Mbps Fiber
SuperStack II Switch 1000 
Ethernet/Fast Ethernet

TX - T4 - FX Integration
Connections between 100BASE-T4, 100BASE-TX,
and 100BASE-FX are made easily through the 3Com
SuperSack II Hub 100 stackable Fast Ethernet hub.
Bridging or routing is not required to connect together
these technologies. The FMS 100 allows stackability of
100BASE-TX and 100BASE-T4 units with centralized
SNMP and RMON Management using the SuperSack II
Hub 100 Management Unit.
100BASE-T Topology Rules
When creating a Fast Ethernet network, it is important to
follow the IEEE 802.3 topology rules. One main difference
between 10BASE-T Ethernet and 100BASE-T Fast Ethernet
is the use of hub (or repeater) classifications. Fast Ethernet
repeaters are either Class I or Class II repeaters depending
on how many “hops” or stacks of repeaters are allowed
in one segment, or collision domain. A Class I repeater
supports 1 repeater or repeater stack in one segment. A
Class II repeater supports up to 2 repeater or repeater stacks
(“hops”) in one segment. Most 100BASE-T4 repeaters
are Class I repeaters.
This diagram shows the topology rules for constructing
a Fast Ethernet network. All distances shown for UTP
cable are the same for 100BASE-TX and 100BASE-T4.
100BASE-T switch or bridge
MAC–MAC
412m fiber
One repeater: 261m
(161m fiber + 100m UTP)
100BASE-T 
Class II hub
100BASE-T Class II hub
NETBuilder II
bridge/router
Floor 100
Floor 50
Floor 25
100BASE-T Class I hub
100m UTP
100m UTP
100m UTP
5m UTP
SuperStack II switch 3000
Two repeaters: 205m
(typically 100m + 
5m + 100m UTP)
Legend
 Shared 100 Mbps
 Switched 100 Mbps
100BASE-T4 Product Overview
■Fast EtherLink 10/100BASE -T4 PCI Network Interface
Card (3C595-T4) 3Com combines the highest performance
10BASE-T and 100BASE-T NIC into one solution with
100BASE-T4 support. With bus mastering technology and
3Com’s patented Parallel Tasking, Fast EtherLink provides
the highest throughput available in either 100BASE-T or
100BASE-T4 modes. Fast EtherLink has a single RJ-45 UTP
connector which allows automatic configuration and connection
to either 10BASE-T or 100BASE-T4 networks. No hardware
or software changes are needed to move between network
speeds - Fast EtherLink automatically senses the speed of the
hub. Fast EtherLink also comes in versions for 10/100BASE-
TX PCI or 10/100BASE-TX EISA. All 3Com NIC come with
integrated network management and a lifetime guarantee.

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SuperStack II Hub 100-T4 Hub (3C250-T4)
3Com adds Category 3 UTP support to the market leading SuperStack II Hub 100. Fully stackable
with SuperStack II Hub 100-TX, the Hub 100-T4 integrates support for Category 3 and Category
4 UTP into new and existing Fast Ethernet workgroups. Along with full 100Mbps throughput over
Category 3, 4 or 5 UTP cabling, optional SNMP and RMON management minimizes troubleshooting
efforts and enhances network availability. Through 3Com’s SuperStack system architecture, the
FMS 100 family provides the industry’s first manageable, stackable, integrated TX/T4 solutions.
Other Fast Ethernet Products from 3Com:
Product Description Order # Interfaces Supported
Fast EtherLink 10/100BASE-TX PCI 3C595-TX 10BASE, 100BASE-TX
10/100BASE-TX PCI NIC
Fast EtherLink 10/100BASE-TX EISA 3C597-TX 10BASE, 100BASE-TX
10/100BASE-TX EISA NIC
SuperStack II Hub Stackable TX hub 3C250-TX/I 100BASE-TX, 100BASE-FX
100 TX
SuperStack II Hub 100 TX optional transceiver 3C252-TX 100BASE-TX
Transceiver Module module
SuperStack II Hub 100 FX optional transceiver 3C262-FX 100BASE-FX
Transceiver Module module
SuperStack II Hub 100 SNMP Management 3C215 N/A
Management Unit
SuperStack II Switch 1000 10-100 workgroup switch 3C16900, 3C16901 10BASE-T, 100BASE-TX,
100BASE-FX, ATM
SuperStack II Switch 3000 100 Mbps switch 3C16942, 3C16941 10BASE-T, 100BASE-TX,
100BASE-FX, ATM
LANPlex 2500 10-100 enterprise switch 3C250100, 3C250200 10BASE-T, 100BASE-TX,
100BASE-FX, FDDI, ATM
NetBuilder II multiprotocol router 3C6000, 3C6001 many (inc. 100BASE-TX
3C6002 and 100BASE-FX)
To learn more about 3Com products, visit our World Wide Web site at http://www.3com.com.
© 3Com Corporation 1995. All rights reserved. 3Com is a publicly owned corporation (NASDAQ: COMS). 3Com, Boundary Routing, LANplex, LinkBuilder, and
NETBuilder are registered trademarks, and FMS, Focus, SuperStack, and Transcend are trademarks of 3Com Corporation. Sniffer is a registered trademark of
Network General Corporation. NetView and OS/2 are registered trademarks of International Business Machines Corporation. HP and OpenView are registered
trademarks of Hewlett-Packard Company. SunNet is a trademark of Sun Microsystems, Inc. UNIX is a registered trademark of UNIX Systems Laboratories, Inc.All
specifications are subject to change without notice.
Printed in U.S.A. on recycled paper. 100255-001
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