HP Procurve 2650 Management And Configuration Manual page 237

Configuring for Network Management Applications
CDP
CDP-Capable Hubs. Some hubs are capable of running CDP, but also
forward CDP packets as if the hub itself were transparent to CDP. Such hubs
will appear in the switch's CDP Neighbor table and will also maintain a CDP
neighbor table similar to that for switches. For more information, refer to the
documentation provided for the specific hub.
Troubleshooting CDP Operation. Turn to "Using the Event Log To Identify
Problem Sources" on page C-21.
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