Understanding LLDP

The QFX Series product uses Link Layer Discovery Protocol (LLDP) to learn and distribute device information on network links. The information enables the switch to identify a variety of devices quickly, resulting in a LAN that interoperates smoothly and efficiently.

LLDP-capable devices transmit information in Type Length Value (TLV) messages to neighbor devices. Device information can include specifics, such as chassis and port identification and system name and system capabilities. The TLVs leverage this information from parameters that have already been configured in the Junos OS software.

The QFX Series products support the following basic TLVs:

• Chassis Identifier—The MAC address associated with the local system.
• Port Identifier—The port identification for the specified port in the local system.
• Port Description—The user-configured port description. The port description can be a maximum of 256 characters.
• System Name—The user-configured name of the local system. The system name can be a maximum of 256 characters.
• System Description—The system description containing information about the software and current image running on the system. This information cannot be configured, but is taken from the software.
• System Capabilities—The primary function performed by the system. The capabilities that system supports are defined; for example, bridge or router. This information cannot be configured, but is based on the model of the product.
• Management Address—The IP management address of the local system.

The QFX Series products support the following 802.3 TLVs:

• Power via MDI—A TLV that advertises media dependant interface (MDI) power support, power source equipment (PSE) power pair, and power class information.
• MAC/PHY Configuration Status—A TLV that advertises information about the physical interface, such as autonegotiation status and support and MAU type. The information can not be configured, but is based on the physical interface structure.
• Link Aggregation—A TLV that advertises whether the port is aggregated and its aggregated port ID.
• Maximum Frame Size—A TLV that advertises the Maximum Transmission Unit (MTU) of the interface sending LLDP frames.
• Port Vlan—A TLV that advertises the VLAN name configured on the interface.