Description

LLDP (Link Layer Discovery Protocol) is defined in IEEE 802.1AB as a layer 2 protocol, which facilitates network and neighbor discovery. Neighbor discovery is made possible through advertisements sent by each network device that is participating in LLDP. Advertisements are sent by LLDP-enabled devices to identify themselves and to announce their capabilities to neighboring devices.

LLDP is somewhat comparable in purpose to Cisco’s CDP. LLDP operates on both Layer 2 and Layer 3 interfaces. Also for operability of the protocol, it doesn't matter whether the port is a trunk port or an access port as the LLDP frames are untagged. This behavior helps the protocol build the network topology regardless of specific configuration parameters assigned to the port.

This article describes the LLDP configuration and monitoring samples.

 

Solution

LLDP agents advertise their identity and capabilities over LLDP TLV (Type Length Value) data units, known as LLDPDUs (LLDP Data Units), which are exchanged with all other neighboring LLDP agents.  LLDP agents store the information learned from neighbors in a local database. LLDP periodically refreshes the local database in order to maintain accurate information for all neighboring LLDP agents.

  • Configuring LLPDU Updates: EX Series switches send periodic LLDP updates to neighboring devices. These updates are advertised every 30 seconds by default. The advertisement-interval range is between 5 and 32768 seconds and is configured at the [edit protocols lldp] hierarchy level. A sample configuration is shown below: 

[edit]
user@switch> show configuration protocols lldp 
advertisement-interval 30;
interface ge-0/0/10.0;

  • LLDP Statistics : The LLDP receiver agent maintains detailed statistic counters for all LLDP-enabled interfaces. The statistic counters include frames received, frames with errors, and unknown TLVs for a given interface. The example below illustrates the statistic counters for both received and transmitted LLDP traffic for all participating interfaces: 

user@switch> show lldp statistics 
Interface     Received   Unknown TLVs  With Errors    Transmitted   Untransmitted
ge-0/0/13.0   2665       0             0              2666          0
ge-0/0/10.0   17106      0             0              17115         0
ge-0/0/2.0    0          0             0              17111         4

 

Modification History

2020-07-10: Article reviewed for accuracy; no changes required; article valid

 

Related Information