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HP 100Base-T Hubs Installation and Reference Guide

2-10 Installing the System

When the 100Base-FX link is set for the full-duplex communications

(i.e., a dedicated connection), cable length should not exceed 2

kilometers. However, when the link is set for half-duplex

communications (i.e., a shared collision domain), cable length should

not exceed 412 meters (IEEE 802.3u). Also cable length could be

limited further by timing constraints depending on what devices exist in

the same shared collision domain. (See preceding section.)

Maximum Segment Length

- In contrast to cascading devices

through hub ports, cascading through the Switch Port Module

breaks up the collision domain. The number of devices that can

be cascaded is therefore theoretically unlimited. However, in

practice, the length of a cascade (even one passing through

Switch Ports, as implemented in the modules) may be limited by

the time-out requirements of the particular applications running

over the network.

Setting the Communication Mode - The 10/100TX and 100FX

Switch Port Modules both support half and full-duplex

communications. The 10/100Base-TX module uses auto-

negotiation to determine the transmission mode for any new

connection made. Note that the module attempts to detect if the

connecting device is using full duplex. If it is not, then the next

test is for half duplex communication. However, if a connected

device does not also support auto-negotiation, and a link cannot

be established using half duplex (i.e., the last state tested by

auto-negotiation), then you must manually set the transmission

mode for the concerned port to full or half duplex via the

VT-100 console interface (Chapter 4). The transmission mode

for the 100Base-FX module must be set manually as the

100Base-FX standard does not support auto-negotiation.

Bridging Functions - The Switch Port Modules form a separate

collision domain from the rest of the ports in the stack. They

therefore provide fully transparent or learning bridging

functions which enable the module to automatically learn node

addresses required to filter and forward traffic based on the

destination address (i.e., traffic is filtered if the destination

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HP 100BaseT Guide de l'utilisateur Page 42