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ELEC 99.05ELEC 99.05Network Topologies & Connections

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Toplogies and ConnectionsToplogies and Connections

• Differing physical topologies yield equivalent ethernet traffic at the workstation.

• For UTP connections, cable type depends on the types of devices connected.

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Bus TopologyBus Topology

Bus

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Extended Star TopologyExtended Star Topology

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Equivalent EthernetsEquivalent Ethernets

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Crossover CableCrossover Cable• Transmit pair “crosses over” to Receive pair.

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Crossover CableCrossover Cable• Connects NIC to NIC.

• Connects hub to hub.

transmit pair

receive pair

transmit pair

receive pair(crossover cable)

transmit pair

receive pair

transmit pair

receive pair(crossover cable)

ACTACT10M100M

1 2 3 4

13 14 15 16

5 6 7 8

17 18 19 20

9 10 11 12

21 22 23 24

UPLINK

1 2 3 4 5 6 7 8 9 101112

131415161718192021222324COLCOL

PWR

SWITCHhubACTACT

10M100M1 2 3 4

13 14 15 16

5 6 7 8

17 18 19 20

9 10 11 12

21 22 23 24

UPLINK

1 2 3 4 5 6 7 8 9 101112

131415161718192021222324COLCOL

PWR

SWITCH hub

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Straight-Through CableStraight-Through Cable• Connects NIC to hub.

transmit pair

receive pair

transmit pair

receive pair

ACTACT10M100M

1 2 3 4

13 14 15 16

5 6 7 8

17 18 19 20

9 10 11 12

21 22 23 24

UPLINK

1 2 3 4 5 6 7 8 9 101112

131415161718192021222324COLCOL

PWR

SWITCHhub(straight through cable)

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Straight-Through CableStraight-Through Cable• When connecting two PCs via a hub,

straight-through cables are used. Where does the crossover occur?

• In the hub!

transmit pair transmit pairACTACT

10M100M1 2 3 4

13 14 15 16

5 6 7 8

17 18 19 20

9 10 11 12

21 22 23 24

UPLINK

1 2 3 4 5 6 7 8 9 101112

131415161718192021222324COLCOL

PWR

SWITCH

receive pair receive pair

hubPC1 PC2(straight through cable) (straight through cable)

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Cabling ExampleCabling Example

Straight - Thru Straight - Thru Straight - Thru

Crossover CrossoverCrossover

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Hub FeatureHub Feature

• Most hubs have a special “uplink port” that can be switched from crossover to straight-through function.

• Usually, the uplink is port 1.• The uplink allows use of straight-

through cables throughout all connections.

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Hubs with UplinkHubs with Uplink

Straight - Thru Straight - Thru Straight - Thru

SwitchableUplink Port

Straight - Thru Straight - Thru

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QuizQuiz

• NIC to NIC - what type cable?• Crossover

• NIC to hub - what type cable?• Straight-through

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QuizQuiz

• Hub to hub - what type cable??• Crossover

• Hub uplink port to hub - what type cable?• Straight-through

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QuizQuiz

• On most hubs, which port is the hub uplink on?• Port 1

• Could I attach a workstation NIC to the uplink port?

• Sure - just use a regular straight-through cable. If necessary, change the setting on the uplink port switch!

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QuizQuiz

• How can I tell if the hub’s uplink port switch is set correctly for the type of cable & device attached?

• Look for link light!