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Configuring for Network Management Applications

CDP

Using the example in figure 14-12, the CDP Neighbors Table for switches “A”

and “B” would appear similar to these:

Switch A:

Switch B:

(Note that no CDP devices appear on port B5, which is connected to a device on which CDP is present, but disabled.)

Figure 14-13. Example of Viewable CDP Neighbors Table for Switches “A” and “B” in Figure 14-6

Thus, based on the CDP packets it receives, each CDP device maintains a per-

port data entry for each of its neighbors that are running CDP, but not for other

CDP devices that are accessible only through a CDP Neighbor. (See the

relationship between switches A, B, and C in figure

14-12.) In other words, a

CDP device will have data on its immediate CDP Neighbors (including those

reached through a device that is transparent to CDP), but not to other CDP

devices in the network.

Table 14-2. How Devices Handle Incoming CDP Packets

Status of Device Receiving

a CDP Packet

Action of Receiving Device

Running CDP Stores neighbor data in CDP Neighbors Table. Does not forward CDP packet.

CDP Disabled Drops CDP packet. There is no CDP Neighbors Table and no CDP Neighbor data is stored.

No CDP Capability Forwards CDP packet out all ports except the port on which the packet was received.

Router Running CDP Stores neighbor data in CDP Neighbors Table. Does not forward CDP packet.

Non-CDP devices (that is, devices that are not capable of running CDP) are

transparent to CDP operation. However, an intervening CDP-aware device

that is CDP-disabled is not transparent. For example, in figure

14-12 (page

14-28), “B”, “D”, and “E” are not CDP Neighbors because “D” (the intervening

CDP-disabled switch) does not forward CDP packets; i.e. is not transparent

to CDP traffic. (For the same reason, switch “E” does not have any CDP

Neighbors.)

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HP 5300 Informações Técnicas Página 293