Management and Configuration Guide K/KA/KB.15.15

model, consult the Release Notes (available on the HP Networking website.) If LLDP has not yet
been implemented (or if you are running an older version of software), consult a previous version
of the Management and Configuration Guide for device discovery details.
LLDP (Link Layer Discovery Protocol) Provides a standards-based method for enabling the switches
covered in this guide to advertise themselves to adjacent
devices and to learn about adjacent LLDP devices.
LLDP-MED (LLDP Media Endpoint
Discovery)
Provides an extension to LLDP and is designed to support
VoIP deployments.
NOTE: LLDP-MED is an extension for LLDP, and the switch requires that LLDP be enabled as a
prerequisite to LLDP-MED operation.
An SNMP utility can progressively discover LLDP devices in a network by:
1. Reading a given device's Neighbors table (in the Management Information Base, or MIB) to
learn about other, neighboring LLDP devices.
2. Using the information learned in step 1 to find and read the neighbor devices' Neighbors
tables to learn about additional devices, and so on.
Also, by using show commands to access the switch's neighbor database for information collected
by an individual switch, system administrators can learn about other devices connected to the
switch, including device type (capability) and some configuration information. In VoIP deployments
using LLDP-MED on the switches, additional support unique to VoIP applications is also available.
See “LLDP-MED” (page 258).
General LLDP operation
An LLDP packet contains data about the transmitting switch and port. The switch advertises itself
to adjacent (neighbor) devices by transmitting LLDP data packets out all ports on which outbound
LLDP is enabled and by reading LLDP advertisements from neighbor devices on ports that are
inbound LLDP-enabled. (LLDP is a one-way protocol and does not include any acknowledgement
mechanism.) An LLDP-enabled port receiving LLDP packets inbound from neighbor devices stores
the packet data in a Neighbor database (MIB.)
LLDP-MED
This capability is an extension to LLDP and is available on the switches. See “LLDP-MED” (page 258).
Packet boundaries in a network topology
• Where multiple LLDP devices are directly connected, an outbound LLDP packet travels only to
the next LLDP device. An LLDP-capable device does not forward LLDP packets to any other
devices, regardless of whether they are LLDP-enabled.
• An intervening hub or repeater forwards the LLDP packets it receives in the same manner as
any other multicast packets it receives. Thus, two LLDP switches joined by a hub or repeater
handle LLDP traffic in the same way that they would if directly connected.
• Any intervening 802.1D device or Layer-3 device that is either LLDP-unaware or has disabled
LLDP operation drops the packet.
LLDP operation configuration options
In the default configuration, LLDP is enabled and in both transmit and receive mode on all active
ports. The LLDP configuration includes global settings, which apply to all active ports on the switch,
and per-port settings, which affect only the operation of the specified ports.
The commands in the LLDP sections affect both LLDP and LLDP-MED operation.
252 Configuring for Network Management Applications