Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) - Manual (Page 1914)

LLDP, LLDP-MED and Voice VLAN Introduction and Configuration
Software Reference for x310 Series Switches
70.10 AlliedWare Plus TM Operating System - Version 5.4.4C C613-50046-01 REV A
Storing LLDP Information
When an LLDP device receives a valid LLDP advertisement from a neighboring network
device, it stores the information in an IEEE-defined Simple Network Management Protocol
(SNMP) Management Information Base (MIB).
LLDP stores information in the LLDP MIB defined in Section 12 of the IEEE Standard
802.1AB-2005, its extensions defined in Annex F, Annex G, and ANSI/TIA-1057- 2006, about:
LLDP-EXT-MED-MIB ANSI/TIA-1057- 2006, Section 13.3, LLDP-MED MIB Definition
■ Local system information. This is the information that LLDP can transmit in
advertisements to its neighbors.
■ Remote systems information. This is the data that the device receives in
advertisements from its neighbors.
■ LLDP configuration. This can be used with SNMP to configure LLDP on the device.
■ LLDP statistics. This includes information about LLDP operation on the device,
including packet and event counters.
This information can be accessed either via SNMP, or directly using the command line
interface.
Local system Information about your device is called local system information. The LLDP local system
MIB maintains this information, which consists of device details, as well as any user-
configured information that you have set up for your switch, for example a port
description or a management address.
LLDP on this device can store one management address per port, and transmit this in
LLDP advertisements. It can store multiple management addresses received from each
neighbor.
Remote systems Information gained from neighboring devices is called remote system information. The
LLDP remote systems MIB maintains this information.
The length of time for which neighbor information remains in the LLDP remote systems
MIB is determined by the Time-To-Live (TTL) value of received LLDPDUs. When it receives
an advertisement from a neighbor, LLDP starts a timer based on the Time To Live (TTL)
information in the advertisement. The Time To Live (TTL) information in an advertisement
is:
TTL=transmit interval x holdtime multiplier. If the TTL elapses, for instance if the neighbor
has been removed, LLDP deletes the neighbor’s information from the MIB. This ensures
that only valid LLDP information is stored.
Whenever a new neighbor is discovered, or an existing neighbor sends an advertisement
with new information that differs from the previous advertisement, for example a new or
changed TLV, a remote tables change event is activated. If SNMP notifications are enabled,
the notification lldpRemTablesChange is sent.
To prevent the remote systems MIB from using large amounts of memory and possibly
affecting the operation of your switch, it limits the number of neighbors it stores
information for to 1600. If it is storing information from 1600 neighbors, and detects any
more neighbors, it is considered to have too many neighbors, and discards
advertisements from the rest. There is no per-port limit to the number of neighbors.
SNMP utilities An SNMP utility can read the Neighbors table MIB (Remote Systems Data in the LLDP MIB)
on a device to find out about the LLDP neighbors it is directly connected to on each port.
Then it can read the Neighbors table MIB on each of these neighbors to find out about
their neighboring LLDP devices, and so on.