Link Layer Discovery Protocol (LLDP) (also known as 802.1ab) is an industry-standard protocol designed to supplant proprietary Link-Layer protocols such as Extreme's Discovery Protocol (EDP) and Cisco Discovery Protocol (CDP). The goal of LLDP is to provide an inter-vendor compatible mechanism to deliver Link-Layer notifications to adjacent network devices.
An LLDP device advertises itself to adjacent (neighbor) devices by transmitting LLDP data packets on all interfaces on which outbound LLDP is enabled and reading LLDP advertisements from neighbor devices on ports on which inbound LLDP is enabled. Inbound packets from neighbor devices are stored in a LLDP Management Information Base (MIB). This information can then be queried by other devices through SNMP.
LLDP information is used by network management tools to create accurate physical network topologies by determining which devices are neighbors and through which interfaces they connect. LLDP operates at layer 2 and requires an LLDP agent to be active on each interface that sends and receives LLDP advertisements. LLDP advertisements can contain a variable number of TLV (type, length, value) information elements. Each TLV describes a single attribute of a device such as: system capabilities, management IP address, device ID, port ID. LLDP is useful in obtaining information about an external power device, such as a Wireless Access Point (WAP).
WAPs are treated as external devices that are configured using the LLDP profile to set up inventory information, (e.g., manufacturer’s name) and LLDP-MED Power extensions, if the device fully supports those extensions, which will designate peak power required by the device.
Moreover, LLDP also supports Time-To-Live (TTL) mechanism which helps prevent loops in redundant networks by limiting the number of hops a packet can travel before being discarded. This ensures efficient use of network resources while improving overall network stability.
LLDP supports a defined set of attributes that it uses to discover neighbor devices and are referred to as TLVs which are as follows:
- Type = Chassis Id, Port Id, Mgt Address, Vendor Specific, ???
- Length = Length of value field in octets (not including pads)
- Value = Binary list of octets + pads for alignment
Devices running LLDP, on one of their interfaces, uses TLVs to receive and send information to their neighbors. These devices store the information of neighboring devices in a local table that can be accessed using Simple Network Management Protocol (SNMP). Information stored by the devices includes:
- System name & description
- Port name & description
- IP management address
- VLAN
- Capabilities of the neighbor device
- MAC address
- MDI power
LLDP-MED
LLDP-MED (ANSI/TIA-1057/D6) extends the LLDP (IEEE 802.1AB) industry standard to support advanced features on the network edge for Voice Over IP (VoIP) endpoint devices with specialized capabilities and LLDP-MED standards-based functionality. LLDP-MED in the switches uses the standard LLDP commands described earlier in this section, with some extensions, and also introduces new commands unique to LLDP-MED operation. The show commands described elsewhere in this section are applicable to both LLDP and LLDP-MED operation. LLDP-MED enables:
- Configure Voice VLAN and advertise it to connected MED endpoint devices.
- Power over Ethernet (PoE) status and troubleshooting support via SNMP.
- LLDP-MED capabilities TLV
- Network policy TLV
- Power management TLV
- Inventory management TLV
- Location TLV
LLDP Frame Format
In LLDP information’s are sent by devices from each of their interfaces at a fixed interval, in the form of an Ethernet frame. Each frame contains one LLDP Data Unit (LLDPDU). Each LLDPDU is a sequence of type-length-value (TLV) structures.
- Ether Type field is set to 0x88cc.
- Each LLDP frame starts with the following mandatory TLVs and must intact in LLDP implementations.
- Chassis ID
- Port ID, and
- Time-to-Live (TTL).
- Any numbers of optional TLVs are followed by mandatory TLVs.
- The frame ends with a special TLV named end of LLDPDU in which both the type and length fields are 0.
- The LLDP specification allows for various organizations to define and encode their own TLVs. These are called Organizationally Specific TLVs. All Organizationally Specific TLVs start with an LLDP TLV Type value of 127.
LLDP Tab
The Profile /Template List of the LLDP profiles contains a list of LLDP profiles on the Panorama PON server that can be applied to any OLT managed by the server. A default profile is provided. This profile is assigned to connections when initially provisioned. The default profile cannot be edited or deleted.
The LLDP tab contains icons used to create, edit, clone, or delete profiles. Additional icons are provided to view the profile status when creating or editing a profile. These icons can be selected from the toolbar or by right-clicking a listed profile and selecting the desired icon.
- To access LLDP right-click on the profiles (
) icon on the Main Window Toolbar.
- For LLDP related procedures, refer to below:
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