4-2
Faulty or Loose Cables
Visually inspect for loose or faulty connections at all connectors and cables. If that does not
correct the problem, try replacing the cable.
Non-standard Cables
Non-standard and incorrectly-wired cables may generate increased network collisions or other
network problems which will impair network performance. A common Category 5 cable tester is
a great tool for troubleshooting network installations and is highly recommended.
Improper Network Design
Verify that your network has been properly designed. Most errors simply result from poor quality
cable, poor cable routing, network congestion, improper cable length, and too many
repeater/hubs between end nodes. Errors may also result from inadvertent data path loops
(redundant message paths). Message loops can generate broadcast storms that can bog down a
network. There should be only one active message path between any two nodes on a network.
Excessive collisions may be indicative of a cable that is too long. It may also signal the presence
of too many repeaters (hubs) between devices and can also be indicative of a congested
network (too many nodes in one segment).
A high number of undersized an fragmented packets can result from interference induced into
the network cable, by either passing it too close to noisy devices, or because of problems with
the network devices themselves. In these instances, check for improper cabling, damaged
cables, or cables routed too closely to noisy equipment or other wiring.
A high number of oversized packets can result from a bad transceiver, excessive cable noise, or
from a speed mismatch between the switch ports and the connected devices.
LED Indicators
The switch can also be visually monitored via its own front-panel LED indicators. This can be
useful to assist in identifying common problems and to help you find possible solutions.
Check the redundant PWR1 and PWR2 LED’s to verify DC power. The PWR LED will light for
any connected power (PWR1, PWR2, or DC-IN).
Check PWR for power via an AC adapter connected to DC-IN. If the power LED indicator does
not light when the power cord is plugged in, you might have a problem with the power outlet, or
the power cord. If the switch simply powers OFF on its own after running for a period of time,
check for loose power connections, power losses, or surges at the power outlet. You should also
verify that your supply voltage remains within the required 12-48VDC range while under load.
Refer to the port Link LED (LNK) to verify that a connection has been properly established (solid
green). A blinking green LNK LED indicates communication activity. If the LNK LED remains off
after making a connection, then no device has been detected and the cable may be bad or the
connected device may be un-powered.
Refer to the Collision LED (COL) to monitor for excessive collisions. A blinking COL LED
indicates that collisions have occurred. This LED will be solid ON for a full duplex connection, as
collisions cannot occur for full-duplex. A full-duplex connection can be achieved by simply
connecting one device per switch port, and this is the most deterministic mode of operation.
