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DS508.fm Page 5 Friday, January 30, 1998 3:46 PM
Cable & Connector Information
Twisted Pair Cables
For two devices to communicate, the transmitter of each device must be
connected to the receiver of the other device. The crossover function is
usually implemented internally as part of the circuitry in the device.
Most repeaters and switch ports are media-dependent interfaces with
crossover ports, referred to as MDI-X or Normal ports. Computers and
workstation adapter cards are usually media-dependent interface ports,
referred to as MDI or Uplink ports.
The figures illustrate the use of straight-through and crossover twisted
pair cables.
Straight-through
Uplink or
twisted pair cable
MDI port
1
Tx
2
3
Rx
6
Normal or
Crossover
MDI-X port
twisted pair cable
1
Rx
2
3
Tx
6
RJ-45 Connector
The RJ-45 connector (shown in the illustration with an RJ-45 plug) is
used to connect workstations, hubs, and switches through unshielded
twisted pair cable. The RJ-45 connector accepts four-pair Category 3 or
Category 5 UTP cable.
12345678
Normal Assignment
RJ-45 Connector
on Ports 1 to 8 or
Pin Assignment
1 to 16
1
Input Receive Data +
2
Input Receive Data -
3
Output Transmit Data +
6
Output Transmit Data -
4, 5, 7, 8
Not used
Normal or
MDI-X port
1
Rx
2
3
Tx
6
Normal or
MDI-X port
1
Rx
2
3
Tx
6
8146EB
8
1
711EA
Uplink Assignment
on Port 8 or 16
Output Transmit Data +
Output Transmit Data -
Input Receive Data +
Input Receive Data -
Not used
Troubleshooting Information
Symptom
Cause
Power LED off
No power at hub
In a stack, no
power at hub but
Terminator LED is
on
Terminator
Cascade cable not
LED of a
connected properly
middle hub in a
stack is on
Link LED off or
Port connection
intermittent
not functioning
Collision LED
Collisions taking
on or blinking
place on network
segment(s)
Problems with
Normal/Uplink
port 8 on the
push button in the
Model DS508
wrong position
hub or port 16
on the Model
DS516 hub
5
Solution
Check the power cord
connections.
Check the power cord. In a
stack, the termination circuitry
gets power from the cascade
cable. If one hub in the stack
has a faulty power cord or the
cord is unplugged, the
Terminator LED remains on and
the remaining hubs in the stack
operate normally.
Check for proper connection.
Check the crimp on the RJ-45
connectors and make sure that
the plug is properly inserted and
locked into the port at both the
hub and device. Make sure
cabling is Category 5 and meets
the requirements for 100 Mbps
operation.
Check installation of the network
interface cards and verify that
they are 100 Mbps capable. Be
sure that the proper software
driver is loaded. Check link
LEDs on the network adapter
card and PC or workstation.
Make sure cables and
connectors are correct.
Collisions are normal on
Ethernet networks. Excessive
collisions can be caused by
incorrect cabling, connectors, or
wiring techniques or can occur
when the network is too busy.
Ensure that the far end is set to
half-duplex mode and is
operating properly. Check for
these problems.
Check the Normal/Uplink push
button on the front panel.
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