Carrier Ethernet Configuration Guide, Cisco IOS XE Release (ASR 903)
Using Link Layer Discovery Protocol in Multivendor Networks
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Using Link Layer Discovery Protocol in Multivendor Networks

Using Link Layer Discovery Protocol in Multivendor Networks

Link Layer Discovery Protocol (LLDP), standardized by the IEEE as part of 802.1ab, enables standardized discovery of nodes, which in turn facilitates future applications of standard management tools such as Simple Network Management Protocol (SNMP) in multivendor networks. Using standard management tools makes physical topology information available and helps network administrators detect and correct network malfunctions and inconsistencies in configuration.

The Cisco implementation of LLDP is based on the IEEE 802.1ab standard.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Information About Using Link Layer Discovery Protocol in Multivendor Networks

IEEE 802.1ab LLDP

IEEE 802.1ab Link Layer Discovery Protocol (LLDP) is an optional link layer protocol for network topology discovery in multivendor networks. Discovery information includes device identifiers, port identifiers, versions, and other details. As a protocol that aids network management, LLDP provides accurate network mapping, inventory data, and network troubleshooting information.

LLDP is unidirectional, operating only in an advertising mode. LLDP does not solicit information or monitor state changes between LLDP nodes. LLDP periodically sends advertisements to a constrained multicast address. Devices supporting LLDP can send information about themselves while they receive and record information about their neighbors. Additionally, devices can choose to turn off the send or receive functions independently. Advertisements are sent out and received on every active and enabled interface, allowing any device in a network to learn about all devices to which it is connected. Applications that use this information include network topology discovery, inventory management, emergency services, VLAN assignment, and inline power supply.


Note


LLDP and Cisco Discovery Protocol can operate on the same interface.


The figure below shows a high-level view of LLDP operating in a network node.

When you configure LLDP or Cisco Discovery Protocol location information on a per-port basis, remote devices can send Cisco medianet location information to the switch. For more information, see the Using Cisco Discovery Protocol module.

Benefits of LLDP

  • Follows IEEE 802.1ab standard.
  • Enables interoperability among multivendor devices.
  • Facilitates troubleshooting of enterprise networks and uses standard network management tools.
  • Provides extension for applications such as VoIP.

How to Configure Link Layer Discovery Protocol in Multivendor Networks

Enabling and Disabling LLDP Globally

LLDP is disabled globally by default. This section describes the tasks for enabling and disabling LLDP globally.

Enabling LLDP Globally

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    lldp{hold time seconds | reinit delay | run | timer rate | tlv-select tlv}

    4.    end


DETAILED STEPS
      Command or Action Purpose
    Step 1 enable


    Example:
    Device> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2 configure terminal


    Example:
    Device# configure terminal
     

    Enters global configuration mode.

     
    Step 3 lldp{hold time seconds | reinit delay | run | timer rate | tlv-select tlv}


    Example:
    Device(config)# lldp run
     

    Enables LLDP globally.

     
    Step 4 end


    Example:
    Device(config)# end
     

    Returns to privileged EXEC mode.

     

    Disabling and Enabling LLDP on a Supported Interface

    LLDP is enabled by default on all supported interfaces. This section describes the tasks for disabling and enabling LLDP on a supported interface.

    Disabling LLDP on a Supported Interface

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    interface type number

      4.    no lldp {tlv-select tlv | receive | transmit}

      5.    end


    DETAILED STEPS
        Command or Action Purpose
      Step 1 enable


      Example:
      Device> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.
       
      Step 2 configure terminal


      Example:
      Device# configure terminal
       

      Enters global configuration mode.

       
      Step 3 interface type number


      Example:
      Device(config)# interface ethernet 0/1
       

      Specifies the interface type and number and enters interface configuration mode.

       
      Step 4 no lldp {tlv-select tlv | receive | transmit}


      Example:
      Device(config-if)# no lldp receive
       

      Disables an LLDP TLV or LLDP packet reception on a supported interface.

       
      Step 5 end


      Example:
      Device(config-if)# end
       

      Returns to privileged EXEC mode.

       

      Setting LLDP Packet Hold Time

      Hold time is the duration that a receiving device should maintain LLDP neighbor information before aging it. Perform this task to define a hold time for an LLDP-enabled device.

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    lldp holdtime seconds

        4.    end


      DETAILED STEPS
          Command or Action Purpose
        Step 1 enable


        Example:
        Device> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.
         
        Step 2 configure terminal


        Example:
        Device# configure terminal
         

        Enters global configuration mode.

         
        Step 3 lldp holdtime seconds


        Example:
        Device(config)# lldp holdtime 100
         

        Specifies the hold time.

         
        Step 4 end


        Example:
        Device(config)# end
         

        Returns to privileged EXEC mode.

         

        Setting LLDP Packet Frequency

        Perform this task to specify an interval at which the Cisco software sends LLDP updates to neighboring devices.

        SUMMARY STEPS

          1.    enable

          2.    configure terminal

          3.    lldp timer rate

          4.    end


        DETAILED STEPS
            Command or Action Purpose
          Step 1 enable


          Example:
          Device> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.
           
          Step 2 configure terminal


          Example:
          Device# configure terminal
           

          Enters global configuration mode.

           
          Step 3 lldp timer rate


          Example:
          Device(config)# lldp timer 75
           

          Specifies the rate at which LLDP packets are sent every second.

           
          Step 4 end


          Example:
          Device(config)# end
           

          Returns to privileged EXEC mode.

           

          Monitoring and Maintaining LLDP in Multivendor Networks

          Perform this task to monitor and maintain LLDP in multivendor networks. This task is optional, and Steps 2 and 3 can be performed in any sequence.

          SUMMARY STEPS

            1.    enable

            2.    show lldp [entry {* | word} | errors | interface [ethernet number]| neighbors [ethernet number| detail]| traffic]

            3.    clear lldp {counters | table}

            4.    end


          DETAILED STEPS
              Command or Action Purpose
            Step 1 enable


            Example:
            Device> enable
             

            Enables privileged EXEC mode.

            • Enter your password if prompted.
             
            Step 2 show lldp [entry {* | word} | errors | interface [ethernet number]| neighbors [ethernet number| detail]| traffic]


            Example:
            Device# show lldp entry *
             

            Displays summarized and detailed LLDP information.

            Note   

            When the show lldp neighbors command is issued, if the device ID has more than 20 characters, the ID is truncated to 20 characters in command output because of display constraints.

             
            Step 3 clear lldp {counters | table}


            Example:
            Device# clear lldp counters
             

            Resets LLDP traffic counters and tables to zero.

             
            Step 4 end


            Example:
            Device# end
             

            Returns to user EXEC mode.

             

            Enabling and Disabling LLDP TLVs

            LLDP TLV support is enabled by default if LLDP is enabled globally and locally on a supported interface. Specific TLVs, however, can be enabled and suppressed.

            Configuration Examples for Link Layer Discovery Protocol in Multivendor Networks

            Feature Information for Link Layer Discovery Protocol in Multivendor Networks

            The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

            Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

            Table 1 Feature Information for Using Link Layer Discovery Protocol in Multivendor Networks

            Feature Name

            Releases

            Feature Information

            IEEE 802.1ab LLDP (Link Layer Discovery Protocol)

            Cisco IOS XE Release 3.8S

            Cisco IOS XE Release 3.9S

            LLDP, standardized by the IEEE as part of 802.1ab, enables standardized discovery of nodes, which in turn facilitates future applications of standard management tools such as SNMP in multivendor networks.

            In Cisco IOS XE Release 3.9S, support was added for the Cisco 903 Series Aggregation Services Routers.

            The following commands were introduced or modified: clear lldp, lldp, and show lldp.