Product Documentation

Configuring Link Layer Discovery Protocol

The Citrix ADC supports the industry standard (EEE 802.1AB) Link Layer Discovery Protocol (LLDP). LLDP is a layer 2 protocol that enables the Citrix ADC to advertise its identity and capabilities to the directly connected devices, and also learn the identity and capabilities of these neighbour devices. Using LLDP, the Citrix ADC transmits and receives information in the form of LLDP messages known as LLDP packet data units (LLDPUs).

An LLDPU is a sequence of type, length, value (TLV) information elements. Each TLV holds a specific type of information about the device that transmits the LLDPDU. The Citrix ADC sends the following TLVs in each LLDPU:

  • Chassis ID
  • Port ID
  • Time-to-live value
  • System name
  • System description
  • Port description
  • System capabilities
  • Management address
  • Port VLAN ID
  • Link aggregation

Note: You cannot specify the TLVs to be sent in LLDP messages.

Citrix ADC interfaces support the following LLDP modes:

  • NONE. The interface neither receives from nor transmits LLDP messages to the directly connected device.
  • TRANSMITTER. The interface transmits LLDP messages to the directly connected device but does not receive LLPD messages from the directly connected device.
  • RECEIVER. The interface receives LLDP messages from the directly connected device but does transmit LLPD messages to the directly connected device.
  • TRANSCEIVER. The interface transmits LLDP messages to and receives LLDP messages from the directly connected device.

The LLDP mode of an interface depends on the LLDP mode configured at the global and the interface levels. The following table shows the modes resulting from the available combinations of global- and interface-level settings: Interface and global level LLDP modes.

Note the following points related to LLDP messages transmitted or received by the Citrix ADC:

  • Transmitting LLDP messages. The Citrix ADC transmits LLDPUs from interfaces that are operating in either TRANSMITTER or TRANSCEIVER LLDP mode.

    Following are the global LLDP transmitting parameters on the Citrix ADC:

    • Timer. Interval, in seconds, between LLDPUs that the Citrix ADC sends to a directly connected device.
    • Holdtime Multiplier. A multiplier for calculating the duration for which the receiving device stores the LLDP information in its database before discarding or removing it. The duration is calculated as the Holdtime Multiplier parameter value multiplied by the Timer parameter value.
  • Receiving LLDP Messages. The Citrix ADC stores the LLDPDU information in its Management Information base (MIB). The stored LLDP information is classified or grouped under the ID of the interface that received the LLDPDU. The Citrix ADC retains this LLDP information for the duration specified in the received LLDPU.

    If the ADC receives another LLDPDU on an interface before the stored LLDP information for that interface is discarded, the ADC replaces the stored LLDP information for that interface with information in the new LLDPDU.

Configuration Steps

Configuring LLDP on a Citrix ADC appliance consists of the following tasks:

  1. Set global level LLDP parameters. In this task, you set the global LLDP parameters such as LLDP Timer, Hold Time Multiplier, and LLDP mode.

  2. Set the interface level LLDP parameters. In this task, you set the LLDP mode for an interface.

  3. (Optional) Display neighbor-device information. You can display the neighbor-device LLDP information collected on all of the Citrix ADC’s interfaces, or just the LLDP information collected on specified interfaces. If you do not specify an interface, the information is shown for all interfaces.

Following are the prerequisites for configuring LLDP on a Citrix ADC:

  1. Make sure that you understand the standard LLDP protocol (IEEE 802.1AB).

  2. Verify that you have configured LLDP on the desired directly connected devices.

CLI procedures

To set global level LLDP parameters by using the CLI:

At the command prompt, type:

  • set lldp param [-[-holdtimeTxMult <positive_integer>][-timer <positive_integer>] [-Mode <Mode>]
  • show lldp param

To configure an interface for LLDP by using the CLI:

At the command prompt, type:

  • set interface <id> -lldpmode <lldpmode>
  • show interface <id>

To display neighbor device information by using the CLI:

At the command prompt, type one of the following commands:

  • show lldp neighbors
  • show lldp neighbors <ifnum>

GUI procedures

To set the global level LLDP parameters by using the GUI:

  1. Navigate to System > Network, and click Configure LLDP Parameters.
  2. Set the following parameters:

    • Hold Timer Multiplier
    • Timer
    • Mode

To configure an interface for LLDP by using the GUI:

Navigate to System > Network > Interfaces, open the interface, and set the LLDP mode parameter.

To display neighbor device information by using the GUI:

Navigate to System > Network > Interfaces and, in the Action list, select View LLDP Neighbors.

LLDP Support in a Cluster Setup

In a cluster setup, the GUI and CLI display the LLDP neighbour configuration of all or specific cluster nodes when the GUI or CLI is accessed through the Cluster IP address (CLIP). Any change made to the global level LLDP mode is applied to the global level LLDP mode on each of the cluster nodes.

Consider an example of a cluster setup of three nodes, NS1, NS2, and NS3. Each of these nodes are connected to both routers Router-1 and Router-2. The following output is displayed when the show lldp neighbor -summary operation is performed on the Cluster CLI that is accessed through the Cluster IP address (CLIP) of the cluster setup. The output shows the LLDP neighbour information of all these nodes.

> show lldp neighbor -summary

Node Id: 1
------------------------------------------------------------
    Interface    ChassisId           PortId     System name
------------------------------------------------------------
1     1/1/1      fe:c7:3b:13:bd:11    1/1         Router-1

2     1/1/2      12:68:7b:9e:4c:11    1/1         Router-2

Node Id: 2
-------------------------------------------------------------
    Interface    ChassisId           PortId     System name
-------------------------------------------------------------
1     2/1/1      fe:c7:3b:13:bd:12    1/2        Router-1

2     2/1/2      12:68:7b:9e:4c:12    1/2        Router-2

Node Id: 3
-------------------------------------------------------------
    Interface    ChassisId            PortId     System name
-------------------------------------------------------------

1     3/1/1       fe:c7:3b:13:bd:13    1/3        Router-1

2     3/1/2       12:68:7b:9e:4c:13    1/3        Router-2

Done

Configuring Link Layer Discovery Protocol