LLDP Test

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.
Host	The IP address of the host for which the test is being configured.
NetScaler Username, NetScaler Password, and Confirm Password	To monitor a ADC device, the eG agent should be configured with the credentials of a user with read-only privileges to the target ADC 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.
SSL	The eG agent collects performance metrics by invoking NITRO (ADC Interface Through Restful interfaces and Objects) APIs on the target ADC 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 ADC 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.	MB	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.	MB
Packets received	Indicates the number of LLDP packets received during the last measurement period.	Number
Packets transmitted	Indicates the number of LLDP packets transmitted during the last measurement period.	Number
Error packets	Indicates the numbernumber of LLDP error packets during the last measurement period.	Number	Ideally, the value of this measure should be 0.
Discarded packets	Indicates the number of LLDP discarded packets during the last measurement period.	Number	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.	Number	Ideally, the value of this measure should be 0.