Hirschmann GREYHOUND GRS1020, Reference Manual

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Operation diagnosis
13.9 Topology discovery
208
UM Config GRS
Release 8.0 09/2019
If you connect the port to devices with the topology discovery function active, then the devices
exchange LLDP Data Units (LLDPDU) and the topology table displays these neighboring devices.
When a port connects only devices without an active topology discovery, the table contains a line
for this port to represent the connected devices. This line contains the number of connected
devices.
The FDB address table contains MAC addresses of devices that the topology table hides for the
sake of clarity.
13.9.2 LLDP-Med
LLDP for Media Endpoint Devices (LLDP-MED) is an extension to LLDP that operates between
endpoint devices. Endpoints include devices such as IP phones, or other Voice over IP (VoIP)
devices or servers and network devices such as switches. It specifically provides support for VoIP
applications. LLDP-MED provides this support using an additional set of common type-length-value
(TLV) advertisement messages, for capabilities discovery, network policy, Power over Ethernet,
inventory management and location information.
The device supports the following TLV messages:

capabilities TLV
Lets the LLDP-MED endpoints determine the capabilities that the connected device supports
and what capabilities the device has enabled.

Network policy TLV
Lets both network connectivity devices and endpoints advertise VLAN configurations and
associated attributes for the specific application on that port. For example, the device notifies a
phone of the VLAN number. The phone connects to a switch, obtain its VLAN number, and then
starts communicating with the call control.
LLDP-MED provides the following functions:

Network policy discovery, including VLAN ID, 802.1p priority and Diffserv code point (DSCP)

Device location and topology discovery based on LAN-level MAC/port information

Endpoint move detection notification, from network connectivity device to the associated VoIP
management application

Extended device identification for inventory management

Identification of endpoint network connectivity capabilities, for example, multi-port IP Phone with
embedded switch or bridge capability

Application level interactions with the LLDP protocol elements to provide timely startup of LLDP
to support rapid availability of an Emergency Call Service

Applicability of LLDP-MED to Wireless LAN environments, support for Voice over Wireless LAN