HP ProCurve 10/100 12 Installation Manual page 23

Troubleshooting
Basic Troubleshooting Tips
3-2
Non-standard cables. Non-standard and miswired cables may cause
network collisions and noise, and can seriously impair network perfor-
mance. 100Base-T networks are more sensitive to miswired cables than
10Base-T networks. 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-T network installation.
Full-duplex link to the hub. Regular hub ports can only operate in half-
duplex mode. If the attached device is running in full-duplex mode, it will
cause a lot of late collisions on the network, degrading performance for
all nodes.
100Base-T topology rules are much more restrictive than 10Base-
T rules. Be aware that you may have to redo existing 10Base-T topology
for 100Base-T products.
When using 100Base-T devices, follow the rules for Category 5 cable
installations.
Some basic Class II 100Base-T Hub rules are displayed here.
• The maximum segment length for a hub-to-end node connection is
100 meters.
• You are permitted to cascade no more than two hubs.
• Do not mix Class I and Class II hubs when cascading.
• When cascading two hubs together, the maximum distance separating
them is 5 meters.
• You must use Category 5 cable installations.
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 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. Refer to the guide entitled Designing HP
ProCurve Workgroup Networks for topology configuration guidelines.
This guide can be found online at the HP World Wide Web site, http://
www.hp.com/go/network_city.
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.