HP Figure 13-10.Example of How the Switch Stores Data on Neighbor CDP Devices

Configuring for Network Management Applications

CDP

General CDP Operation

The switch stores information about adjacent CDP devices in a CDP Neigh­ bors 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 "A"

with CDP Running

CDP Neighbor Table

Switch "C" data

Switch "B"

with CDP Running CDP Neighbor Table Switch "C" data

Switch "C"

with CDP Running

CDP Neighbor Table

Switch "A" data

Switch "B" data

Switch "D" data

Switch "D"

with CDP Running CDP Neighbor Table Switch "C" data

•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 Neighbor table includes data only on neighbor CDP devices, but not on that switch itself.

Figure 13-10. Example of How the Switch Stores Data on Neighbor CDP Devices

Outgoing Packets

A switch running CDP periodically transmits a one-hop CDP packet out each of its ports. This packet contains data describing the switch and, if the one- hop destination is another device running CDP, the receiving device stores the sending device’s data in a CDP Neighbors table. The receiving device also transmits a similar one-hop CDP packet out each of its ports to make itself known to other CDP devices to which it is connected. Thus, each CDP device in the network provides data on itself to the CDP neighbors to which it is directly connected. However, there are instances where a packet is forwarded beyond the immediate neighbor, or simply dropped.

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