HP 6120XG HP ProCurve Series 6120 Blade Switches Installation and Getting Star - Page 31

Basic Troubleshooting Tips 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 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 switch behaves in this way (in compliance 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 switch 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 or compare your cable to the cable in appendix B, "Cables and Connectors" for pinouts and correct cable wiring. A category 5 cable tester is a recommended tool for every 100Base-TX and 1000Base-T network installation. ■ Improper Network Topologies. It is important to make sure you have a valid network topology. Common topology faults include excessive cable length and excessive repeater delays between end nodes. If you have network problems after recent changes to the network, change back to the previous topology. If you no longer experience the problems, the new topology is probably at fault. Sample topologies are shown at the end of chapter 2 in this book, and some topology configuration guidelines can be found online on the HP Web site at www.hp.com/go/bladesystem/documentation. In addition, you should make sure that your network topology contains no data path loops. Between any two end nodes, there should be only one active cabling path at any time. Data path loops will cause broadcast storms that will severely impact your network performance. For your switch, if you wish to build redundant paths between important nodes in your network to provide some fault tolerance, you should enable Spanning Tree Protocol support on the switch. This ensures only one of the redundant paths is active at any time, thus avoiding data path loops. Spanning Tree can be enabled through the switch console, the web browser interface, or ProCurve Manager. The Switch also supports Trunking, which allows multiple network cables to be used for a single network connection without causing a data path loop. For more information on Spanning Tree and Trunking, see the Management and Configuration Guide for the Series 6120 Switches, which is on the HP Web site at www.hp.com/go/bladesystem/documentation. 23