ProCurve Series 2300 and 2500 Switches Release Notes

187
Enhancements in Release F.02.02
CDP
Outgoing Packets
A Series 2500 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.
Figure 86. Example of Outgoing CDP Packet Operation
Incoming CDP Packets
When a CDP-enabled Series 2500 switch receives a CDP packet from another CDP device, it enters
that device’s data in the CDP Neighbors table, along with the port number where the data was received
(and does not forward the packet). The switch also periodically purges the table of any entries that
Switch "A"
Series 2500 Switch
with CDP Running
and Forwarding CDP
Packets to Down-
stream Devices
Switch "B"
CDP-Aware
Switch with
CDP Running
Switch "C"
CDP-Aware
Switch with
CDP Disabled
Router "Y"
With CDP
Disabled or
Nonexistent
Device "Z"
Hub or Other
Non-CDP
Device
Router "X"
With CDP
Running
Accepts, but does not forward CDP
packets describing Switch "A". Also
transmits CDP packets describing itself
(Switch "B") out all ports.
Drops CDP packets describing Switch "A".
Also does not transmit any CDP packets
describing itself (Router "Y").
Forwards CDP packets from Switch "A" out
all ports (except the port receiving the
packets from "A") without any awareness
of CDP operation.
Drops CDP packets describing Switch
"A". Also, does not transmit any CDP
packets describing itself (Switch "C").
Accepts, but does not forward CDP
packets from Switch "A". Also transmits
CDP packets describing itself (Router "X")
out all ports.