refresh-interval
is large. See
Changing the time-to-live for transmitted advertisements (CLI)
on page
225.
Mandatory TLVs
All mandatory TLVs required for LLDP operation are also mandatory for LLDP-MED operation.
LLDP and CDP data management
This section describes points to note regarding LLDP and CDP (Cisco Discovery Protocol) data received by the
switch from other devices. LLDP operation includes both transmitting LLDP packets to neighbor devices and
reading LLDP packets received from neighbor devices. CDP operation is limited to reading incoming CDP
packets from neighbor devices. (switches do not generate CDP packets.)
Incoming CDP and LLDP packets tagged for VLAN 1 are processed even if VLAN 1 does not contain any ports.
VLAN 1 must be present, but it is typically present as the default VLAN for the switch.
NOTE:
The switch may pick up CDP and LLDP multicast packets from VLAN 1 even when CDP-
and /or LLDP-enabled ports are not members of VLAN 1.
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
advertisements, and stores the data from both types of advertisements in its neighbor database. (The switch
stores
only 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 or by using the
show lldp
commands. Take note of the
following rules and conditions:
• If the switch receives both LLDP and CDP advertisements on the same port from the same neighbor, the
switch stores this information as two separate entries if the advertisements have different chassis ID and port
ID information.
• 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 advertisements received from the same device is the same.
• 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 LLDP System
Capability fields.
◦ System Name and Port Descr are not communicated by CDP, and thus are not included in the switch's
Neighbors database.
NOTE:
Because switches do not generate CDP packets, they are not represented in the CDP data
collected by any neighbor devices running CDP.
A switch with CDP disabled forwards the CDP packets it receives from other devices, but does not
store the CDP information from these packets in its own MIB.
248
Aruba 2930F / 2930M Management and Configuration Guide
for ArubaOS-Switch 16.08
