The Citrix ADC supports the industry standard (IEEE 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.

If a TLV contains information that the ADC cannot recognize, it could result in a discovery failure. This is why, it is imperative that administrators are notified when the ADC receives/transmits such erroneous TLVs. This is exactly what the LLDP test does!

This test tracks the data and packet transmissions and receptions over LLDP, scans the TLV elements contained within each LLDPU that is processed, and alerts administrators if any TLV holds information that is not recognized. In the process, the test also measures the LLDP workload on the appliance, and warns administrators of any potential overload. Error packets are also captured and reported.

Target of the test : A Citrix ADC VPX/MPX

Agent deploying the test : A remote agent

Outputs of the test : One set of results for the Citrix ADC VPX/MPX appliance being monitored.

Configurable parameters for the test
Parameter Description

Test Period

How often should the test be executed.


The IP address of the host for which the test is being configured.

NetScaler Username, NetScaler Password, and Confirm Password

To monitor a NetScaler device, the eG agent should be configured with the credentials of a user with read-only privileges to the target NetScaler device. Specify the credentials of such a user in the NetScaler Username and NetScaler Password text boxes. Then, confirm the password by retyping it in the Confirm Password text box.


The eG agent collects performance metrics by invoking NITRO (NetScaler Interface Through Restful interfaces and Objects) APIs on the target NetScaler device. Typically, the NITRO APIs can be invoked through the HTTP or the HTTPS mode. By default, the eG agent invokes the NITRO APIs using the HTTPS mode. This is why, the SSL flag is set to Yes by default. If the target NetScaler device is not SSL-enabled, then the NITRO APIs can be accessed through the HTTP mode only. In this case, set the SSL flag to No.

Measurements made by the test
Measurement Description Measurement Unit Interpretation

Data received

Indicates the LLDP data received during the last measurement period.


These measures are good indicators of the current LLDP workload on the appliance. If the value of one/more of these measures increase consistently, it could signal an overload condition.




Data transmitted

Indicates the LLDP data transmitted during the last measurement period.


Packets received

Indicates the number of LLDP packets received during the last measurement period.


Packets transmitted

Indicates the number of LLDP packets transmitted during the last measurement period.


Error packets

Indicates the numbernumber of LLDP error packets during the last measurement period.


Ideally, the value of this measure should be 0.

Discarded packets

Indicates the number of LLDP discarded packets during the last measurement period.


An abnormally high value for this measure indicates that a large number of packets have been discarded.

Typically, a packet is discarded/remove from the receiver's database upon the expiry of the duration that is computed as a product of the configured Hold Time Multiplier (holdtimeTxMult) and the configured Timer (timer) - i.e., holdtimeTxMult*timer. One of the common causes for an unusually large number of packets getting discarded is the incorrect configuration of the holdtimeTxMult and/or timer parameters. By reconfiguring these parameters, you can control the unnecessary removal of packets from the database.

Not recognized TLVs

Indicates the number of LLDP not recognized TLVs during the last measurement period.


Ideally, the value of this measure should be 0.