HP ProCurve 420 Installation And Getting Started Manual page 40

Troubleshooting
Basic Troubleshooting Tips
For more information on possible network problems and their solutions, refer
to the technical note "Troubleshooting LAN Performance and Intermittent
Connectivity Problems", which can be found on the HP Procurve web site,
http://www.hp.com/go/hpprocurve, in the Information Library section.
4-2
• If the connected device has a fixed configuration, for example
100 Mbps, at half or full duplex, the access point will automatically
sense the link speed, but will default to a communication mode of half
duplex.
Because the AP 420 ww/na behaves in this way (in compliance with
the IEEE 802.3 standard), if a device connected to the access point has
a fixed configuration at full duplex, the device will not connect correctly
to the access point. The result will be high error rates and very inefficient
communications between the access point and the device.
Make sure that all devices connected to the AP 420 ww/na are config-
ured 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, "Access Point Port and Network Cables"
for pinouts and correct cable wiring. A category 5 cable tester is a
recommended tool for every 100Base-TX 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 at the HP Procurve web site, http://www.hp.com/go/
hpprocurve.
Mobile users cannot connect to the network. Make sure that the
access point and wireless clients are configured to the same WEP setting,
SSID, and authentication algorithm. Check to ensure that the wireless
client is within the maximum range supported by the access point. Also
verify that the wireless client has been configured with an IP address
compatible with the attached network, either manually or via DHCP.