Extreme Networks ExtremeWare XOS 11.3, Руководство пользователя

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ExtremeWare XOS 11.3 Concepts Guide
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6 Link Layer Discovery Protocol
This chapter covers the following topics:
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Overview on page 147
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LLDP Messages on page 148
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Managing LLDP on page 150
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Supported TLVs on page 150
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Configuring LLDP on page 156
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Displaying LLDP Settings on page 160
Overview
Beginning with ExtremeWare XOS version 11.2, the software supports the Link Layer Discovery
Protocol (LLDP). LLDP is a Layer 2 protocol (IEEE standard 802.1ab) that is used to determine the
capabilities of devices such as repeaters, bridges, access points, routers, and wireless stations.
ExtremeWare XOS version 11.2 LLDP support enables devices to advertise their capabilities and media-
specific configuration information and to learn the same information from the devices connected to it.
The information is represented in Type Length Value (TLV) format for each data item. The 802.1ab
specification provides detailed TLV information. The TLV information is contained and transmitted in
an LLDP protocol data unit (LLDPDU). Certain TLVs are mandatory and are always sent once LLDP is
enabled; other TLVs are optionally configured. LLDP defines a set of common advertisement messages,
a protocol for transmitting the advertisements, and a method for storing the information contained in
received advertisements.
LLDP provides a standard method of discovering and representing the physical network connections of
a given network management domain. LLDP works concurrently with Extreme Discovery Protocol
(EDP); it also works independently, you do not have to run EDP to use LLDP. The LLDP neighbor
discovery protocol allows you to discover and maintain accurate network topologies in a multivendor
environment.
The information distributed using LLDP is stored by its recipients in a standard Management
Information Base (MIB), making it possible for the information to be accessed by a Network
Management System (NMS) using a management protocol such as the Simple Network Management
Protocol (SNMP).
LLDP transmits periodic advertisements containing device information and media-specific configuration
information to neighbors attached to the same network. LLDP agents cannot solicit information from
other agents by way of this protocol. The TLV format with link layer control frames is used to
communicate with other LLDP agents. LLDP agents also receive link layer control frames, extract the
information from TLVs, and store them in LLDP MIB objects.
If the information values from the device change at any time, the LLDP agent is notified. The agent then
sends an update with the new values, which is referred to as a triggered update. If the information for
multiple elements changes in a short period, the changes are bundled together and sent as a single
update to reduce network load.