UNICOM Electric GST-2402 - Manual (Page 28)

5. Troubleshooting
This section is intended to help you solve the most common problems of the
SmartGST-2402.
Incorrect connections
These ports can auto-detect straight or crossover cables when you link this
switch with other Ethernet device. Always use the correct UTP or STP RJ-45
cable. 10/100Mbps ports (Fast Ethernet) use two pair cable and 1000T ports
(Gigabit Ethernet) use four pair cable. If the RJ-45 connector pins are not at
right position then the link will fail. For fiber connections, please notice that
fiber cable mode and fiber module should be match.
Faulty or loose cables
Look for loose or obviously faulty connections. If they appear to be OK, make
sure the connections are snug. If that does not correct the problem, try a
different cable.
Non-standard cables
Non-standard and miswired cables may cause numerous network collisions
and other network problem and can seriously impair network performance. A
Category 5 cable tester is a recommended tool for every 100Base-T network
installation.
Improper Network Topologies
It is important to make sure that you have a valid network topology. Common
topology faults include excessive cable length and too many repeaters (hubs)