ProCurve Series 2300 and 2500 Switches Release Notes

195
Enhancements in Release F.02.02
CDP
Changing the Hold Time (CDP Packet Time-To-Live) for a Switch’s CDP Packet
Information. The default hold time for the switch’s CDP packet information in the CDP Neighbors
table of another CDP device is 180 seconds (range: 5 - 254). This parameter is controlled in the
transmitting switch, and applies to all outbound CDP packets the switch transmits.
Syntax: cdp holdtime < 5 . . 254 >
For example, to configure a switch’s outbound CDP packets to live for one minute in the CDP
Neighbors table of neighboring CDP devices:
HP2512(config) cdp holdtime 60
Effect of Spanning Tree (STP) On CDP Packet Transmission
If STP has blocked a port on the switch, that port does not transmit CDP packets. However, the port
still receives CDP packets if the device on the other end of the link has CDP enabled. Thus, for
example, if switch "A" has two ports linked to switch "B" (a CDP neighbor and the STP root device)
and STP blocks traffic on one port and forwards traffic on the other:
■ Switch "A" sends outbound CDP packets on the forwarding link, and the switch "B" CDP
Neighbors table shows switch "A" on only one port.
■ Switch "B" sends outbound CDP packets on both links, and the switch "A" CDP Neighbors
table shows switch "B" on both ports.
To summarize, in a CDP neighbor pair running STP with redundant links, if one of the switches is the
STP root, it transmits CDP packets out all ports connecting the two switches, while the other switch
transmits CDP packets out only the unblocked port. Thus, the STP root switch will appear on multiple
ports in the non-root switches CDP Neighbors table, while the non-root switch will appear on only
one port in the root switch’s CDP Neighbors table.
How CDP Selects the CDP Neighbor’s IP Address When Multiple
VLANs Are Present
When a switch detects a CDP neighbor and there are multiple VLANs configured on the neighbor’s
port, the switch uses the following criteria to determine which IP address to use when listing the
neighbor in the CDP Neighbor table:
1. If only one VLAN on the neighbor’s port has an IP address, the switch uses that IP address.
2. If the Primary VLAN on the neighbor’s port has an IP address, the switch uses the neighbor’s
Primary VLAN IP address.