Black Box 24 + or 48 + 4-Port Gigabit Managed Switch with SFP+ 10G Appendix B Troubleshooting

Appendix B: Troubleshooting

Appendix B. Troubleshooting

B.1 Basic Troubleshooting Tips

Most problems are caused by the following situations. Check for these items first when starting your troubleshooting:

Connecting to devices that have a fixed full-duplex configuration.

The RJ-45 ports are configured as “Auto,” that is, when connecting to the attached devices, the switch will operate in one of two ways to determine the link speed and the communication mode (half-duplex or full-duplex):

•If the connected device is also configured to Auto, the switch will automatically negotiate both link speed and communication mode.

•If the connected device has a fixed configuration, for example 100 Mbps, at half or full duplex, the switch will automatically sense the link speed, but will default to a communication mode of half-duplex.

Because the LGB5028A and LGB5052A switches comply with the IEEE 802.3 standard, if a device connected to the switch has a fixed configuration at full-duplex, the device will not connect correctly to the switch. The result will be high error rates and very inefficient communications between the switch and the device.

Make sure all devices connected to the LGB5028A and LGB5052A switches are configured to auto negotiate, or are configured to connect at half-duplex (all hubs are configured this way, for example).

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 network collisions and other network problems, and can seriously impair network performance. Use a new, correctly wired cable. For pinouts and correct cable wiring, we recommend using a Category 5 cable tester for every 100BASE-TX and 1000BASE-T network installation.

Improper network topologies.

Make sure you have a valid network topology. If you switch to a new topology and experience problems, the new topology is probably at fault. In addition, you should make sure that your network topology contains no data path loops.

Check the port configuration.

A port on your switch may not be operating as you expect because it has been put into a “blocking” state by Spanning Tree, GVRP (automatic VLANs), or LACP (automatic trunking).

NOTE: Normal operation of the Spanning Tree, GVRP, and LACP features may put the port in a blocking state. Or, the port just may have been configured as disabled through software.

LGB5028A User‘s Manual

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