General Cdp Operation - HP ProCurve 6400cl Series Management And Configuration Manual

Switch "A"
with CDP Running
CDP Neighbors Table
Switch "C" data
Switch "B"
with CDP Running
CDP Neighbors Table
Switch "C" data
Figure 14-21. Example of How the Switch Stores Data on Neighbor CDP Devices

General CDP Operation

The switch stores information about CDP neighbors in a CDP Neighbors Table
maintained in the switch's MIB (Management Information Base). This data is
available to SNMP-based applications designed to read CDP data from the
MIB. For example:
Switch "C"
with CDP Running
CDP Neighbors Table
Switch "A" data
Switch "B" data
Switch "D" data
Switch "D"
with CDP Running
CDP Neighbors Table
Switch "C" data
Outgoing Packets
A Series 5300xl switch running CDP periodically transmits a CDP packet out
each of its ports. This packet contains data describing the switch and, if the
packet arrives at another device running CDP, the receiving device stores the
sending device's data in a CDP Neighbors table and the packet is not forwarded
to any other devices. The receiving device also transmits a similar CDP packet
out each of its ports to make itself known to other CDP devices to which it is
connected. If there is an intervening device that either has CDP disabled, or
does not have CDP capability, this device receives the inbound CDP packet
and forwards it (floods it out all ports except for the inbound port). In this
case, the CDP packet ceases to be forwarded when it reaches either a CDP-
aware device or an end node. Thus, each CDP device in the network provides
data on itself to the first CDP Neighbor it can reach from each port or trunk
group.
Configuring for Network Management Applications
CDP on the Series 5300xl Switches
• The Neighbors Table in switches "A", "B", and "D"
contain information on switch "C" only because
it is the only neighbor for these switches.
• The Neighbors Table in switch "C" contains
information on switches "A", "B", and "D"
because all of these switches are neighbors of
switch "C".
Note: A given switch's CDP Neighbors Table
includes data only on neighbor CDP devices, but
not on that switch itself.
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