HP procurve series 4100gl Management And Configuration Manual page 228

Configuring for Network Management Applications
CDP
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 10-8. Example of Viewable CDP Neighbor Table for Switches "A" and "B in Figure 10-2
Table 10-1. How Devices Handle Incoming CDP Packets
Status of Device Receiving
a CDP Packet
Running CDP
CDP Disabled
No CDP Capability
Router Running CDP
Router with CDP (1) Disabled
or (2) Not CDP-Capable
10-18
Using the example in figure 10-7, the CDP Neighbor table for switches "A" and
"B" would appear similar to these:
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 10-7.) 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.
Action of Receiving Device
Stores neighbor data in CDP Neighbor table. Does not forward CDP packet.
Drops CDP packet. There is no CDP Neighbor table and no CDP neighbor data is stored.
Forwards CDP packet out all ports except the port on which the packet was received.
Stores neighbor data in CDP Neighbor table. Does not forward CDP packet.
Drops 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 10-7 (page
10-17), "B", "D", and "E" are not CDP neighbors because "D" (the intervening