HP 24S Guide de l'utilisateur télécharger pdf (Page 14)

Port LEDs (green), one for each network port, are ON when the corresponding port is

enabled and functioning normally. Ports can be enabled and disabled using the Port

command on the hub’s console. The AUI port LED is always ON when that port is

enabled, even if it is not being used. For the twisted-pair ports the LED will be OFF if the

link beat signal is not received from the device connected to that port. Each Port LED will

FLASH if the port has been auto-segmented (see “Auto-Segmentation” later in this

chapter).

To view the twisted-pair port LEDs on the HP EtherTwist Hub Plus/48, press the Group

Selector button until the port group you wish to view (group A, B, C, or D) is displayed.

The group selector LED identifies which port group is being displayed by the twisted-pair

port LEDs.

How the Hub Works

The HP EtherTwist Hub/12, Hub Plus, and Hub Plus/48 are multiport repeaters. Data

signals coming into the hub from any of its ports are automatically regenerated and

transmitted to all the other hub ports. The hub regenerates the data without interpreting

the contents, so it can be used in either IEEE 802.3 or Ethernet networks and with any

upper-level protocol.

Collision Detection

These hubs also perform collision detection. A collision occurs when two nodes try to

transmit at the same time. When the hub detects this, it stops repeating the colliding

transmissions and starts transmitting a jamming signal. The jamming signal tells the

transmitting nodes that a collision has occurred. The colliding nodes then stop

transmitting for a random amount of time before attempting to retransmit the data. Once

the collision condition is removed, the hub stops transmitting the jamming signal and

normal operation is restored.

1-6 Introducing the HP EtherTwist Hub/12, Hub Plus, and Hub Plus/48

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HP 24S Guide de l'utilisateur Page 14