Cl Switches - HP ProCurve 6400cl Series Management And Configuration Manual

Configuring for Network Management Applications
LLDP (Link-Layer Discovery Protocol)
14-32
LLDP and CDP Data Management on the Series 3400cl
and 6400cl Switches
This section applies only to the Series 3400cl and 6400cl switches.
LLDP (Link-Layer Discovery Protocol) operation on the 3400cl and 6400cl
switches includes transmitting LLDP packets to neighbor devices and reading
LLDP packets received from neighbor devices. CDP operation on these
switches is limited to reading incoming CDP packets from neighbor devices.
(These switches do not generate CDP packets.) This section describes points
to note regarding LLDP and CDP data received by a 3400cl or 6400cl switch
from other devices.
LLDP and CDP Neighbor Data. With both LLDP and (read-only) CDP
enabled on a switch port, the port can read both LLDP and CDP advertise­
ments, and stores the data from both types of advertisements in its neighbor
database. (The switch only stores CDP data that has a corresponding field in
the LLDP neighbor database.) The neighbor database itself can be read by
either LLDP or CDP methods. If the switch receives both LLDP and CDP
advertisements on the same port from the same neighbor, it stores this
information as two separate entries if the advertisements have differences
chassis ID and port ID information. However, if the chassis and port ID
information are the same, the switch stores this information as a single entry.
That is, LLDP data overwrites the corresponding CDP data in the neighbor
database if the chassis and port ID information in the LLDP and CDP adver­
tisements received from the same device is the same. Note that data read from
a CDP packet does not support some LLDP fields, such as "System Descr",
"SystemCapSupported", and "ChassisType". For such fields, LLDP assigns
relevant default values. Also:
The LLDP "System Descr" field maps to CDP's "Version" and "Platform"
■
fields.
■ The switch assigns "ChassisType" and "PortType" fields as "local" for both
the LLDP and the CDP advertisements it receives.
■ Both LLDP and CDP support the "System Capability" TLV. However, LLDP
differentiates between what a device is capable of supporting and what it
is actually supporting, and separates the two types of information into
subelements of the System Capability TLV. CDP has only a single field for
this data. Thus, when CDP System Capability data is mapped to LLDP, the
same value appears in both of LLDP's System Capability fields.
■ System Name and Port Descr are not communicated by CDP, and thus are
not included in the switch's Neighbors database.