Overview of LLDP in Oracle Solaris

LLDP advertises information throughout a LAN for purposes of topology discovery. With this protocol, a system can advertise connectivity and management information to other systems on the network. This information can include system capabilities, management addresses, and other information relevant to network operations. This protocol also enables that same system to receive similar information about other systems that are on the same local network.

In Oracle Solaris, LLDP is also used to exchange data center bridging exchange protocol (DCBX) TLV units. DCBX provides configuration information about DCB features such as priority-based flow control (PFC) and enhanced transmission selection (ETS). For more information about DCB, see Chapter 8, Working With Data Center Bridging Features in Oracle Solaris.

With LLDP, the system administrator can easily detect faulty system configurations, particularly in complex networks that include virtual local area networks (VLANs), link aggregations, and so on. Information about the topology can be obtained readily without requiring to trace physical connections between servers, switches, and other devices that comprise the network.

Components of an LLDP Implementation

LLDP is implemented with the following components:

• The LLDP package must be installed to enable the LLDP feature. This package delivers the LLDP daemon, command-line utilities, the service manifest and scripts, and other components that are required for LLDP to operate.

• The lldp service is enabled by the svcadm command. This service manages the LLDP daemon and is responsible for starting, stopping, restarting, or refreshing the daemon. This service is automatically enabled after you install the LLDP package.

• The lldpadm command administers LLDP on individual links and is used, for example, to configure the operating mode of LLDP, to specify Type-Length-Value (TLV) units that will be transmitted, and to configure DCBX TLV units. Specifically, the command is used to set per-agent LLDP properties as well as global LLDP properties. The general subcommands of the lldpadm command parallel the subcommands of the dladm and ipadm commands.

  • lldpadm set-* specifies the action to be performed in which one or more values are set for a given LLDP property.

  • lldpadm show-* displays the values that are set for a specified LLDP property.

  • lldpadm reset-* resets the configuration of a specified LLDP property to its default values.

  Use of these subcommands is illustrated in subsequent sections. For more information about the lldpadm command, refer to the lldpadm(1M) man page.

• The LLDP library (liblldp.so) provides APIs that can be used to retrieve LLDP information on a link, to parse LLDP packets, and to perform other functions.

• LLDP agents are LLDP instances that are associated with the network interface card where LLDP is enabled. An LLDP agent controls LLDP behavior on an associated NIC. LLDP agents can be configured only on NICs or physical links and uses the ports of these links to advertise information. Thus, in this LLDP documentation, the name of the LLDP agent, the physical link on which it is enabled, and the port are identical.

• The LLDP daemon (lldpd) manages the LLDP agents on the system. It also interacts with snmpd, the daemon for the Simple Network Management Protocol (SNMP), to retrieve LLDP information that is received on the system through SNMP. In addition, the daemon posts LLDP sysevents information as well as responds to queries from the LLDP library.

Information Sources of the LLDP Agent

The LLDP agent transmits as well as receives LLDP data units (LLDPDUs). The agent manages and stores the information contained in these LLDPDUs in two types of data stores:

• Local management information base, or local MIB - This data store contains network information that pertains to a system's specific link on which the LLDP agent is enabled. A local MIB contains both common and unique information. For example, the chassis ID is common information that is shared among all the LLDP agents on the system. However, port IDs for the system's datalinks are different. Thus, each agent manages its own local MIB.

• Remote MIB - Information in this data store is received from LLDP agents of peer hosts.

LLDP Agent Modes of Operation

The LLDP agent operates in the following modes:

• Transmit only (txonly): In this mode, the LLDP agent does not process incoming LLDPDUs. Therefore, the remote MIB is empty.

• Receive only (rxonly): In this mode, the agent processes only incoming LLDPDUs and stores the information in remote MIBs. However, no information from the local MIB is transmitted.

• Transmit and receive (both): In this mode, the agent transmits local information and processes incoming LLDPDUs and thus, maintains both local and remote MIBs. If the underlying link supports DCB features, DCBX TLV units are automatically enabled for the supported DCB features.

• Disabled (disable): In this mode, the agent does not exist.

SMF Property for LLDP

The service management facility (SMFS) property auto-enable-agents controls how LLDP is enabled on the system. With this property, you can choose to enable LLDP globally across all the physical links or only one physical link at a time. The property can have one of three possible values:

• yes is the default value of the SMF property. With this value, LLDP is enabled globally on all ports in both Rx and Tx modes, provided that no previous LLDP configuration exists on a port. If a configuration exists on a port, then that port's configuration is retained. For example, if a port has been previously configured with LLDP in Rx mode only, then the LLDP service will not switch the agent to run in Rx and Tx modes. LLDP on that port continues to be in Rx mode.

• force enables LLDP in both Rx and Tx modes on all ports and overrides any existing LLDP configurations on any port. For example, if a previous LLDP configuration on a port runs in Rx mode only, the LLDP agent is switched to run in both Rx and Tx modes, which is the default LLDP mode.

• no disables automatic enabling of LLDP on all ports except those with existing LLDP configurations. On these ports, existing LLDP configuration is retained.

Note that each time you customize the auto-enable-agents property, you must restart the LLDP SMF service for the new value to become effective.