SD-WAN ARPs Test

The Citrix SD-WAN appliance uses Address Resolution Protocol (ARP) to resolve the network layer addresses such as IPv4 addresses, into a link layer physical addresses such as MAC address, while handling traffic among multiple hosts on the network. For this purpose, the target appliance has an ARP look-up table that is populated with the IP addresses of the configured hosts and their equivalent MAC addresses. Lets say, if Host A wants to send a request to Host B in the SD-WAN environment, the request first reaches the target SD-WAN appliance. The appliance then starts looking into the ARP table to see if the MAC address for Host B already exists. If the IP address of Host B is available and active in the table, then the appliance will quickly pass the request to Host B and transfer the response received from Host B to Host A. If the IP address of Host B is not available in the table, then appliance will not be able to route the request to Host B. In such a case, Host A will send a broadcast packet to all hosts in the network using the ARP protocol. Now, the host (Host B) which owns the requested IP will respond to the broadcast with a unicast ARP reply to Host A. Sending the broadcast packet and getting response will take more time than directly receiving response from the destination. Therefore, it is necessary for administrators to know the availability status of the IP addresses in the ARP table to ensure fastest communication among the hosts. This is where the SD-WAN ARPs test helps!

This test auto-discovers the IP addresses stored in the ARP lookup table of the target Citrix SD-WAN appliance, and for each IP address, reports the current status. With the help of this measure, administrators can quickly find out whether the monitored IP address is active/dead/inactive in the look-up table and take remedial actions if the IP address is in the bad/inactive/dead state. In the process, this test also reveals the time taken for receiving the response for each IP address. This revelation will help administrators to figure out how quickly the requests are processed and investigate the abnormalities if the response is received with noticeable delay.

Target of the test : A Citrix SD-WAN

Agent deploying the test : A remote agent

Outputs of the test : One set of results for each IP address stored in the ARP look-up table of the Citrix SD-WAN appliance being monitored.

Configurable parameters for the test
Parameter Description

Test Period

How often should the test be executed. By default, this is set to 5 minutes.

Host

The IP address of the target SD-WAN appliance for which this test is to be configured.

Port

Refers to the port at which the target SD-WAN listens to. By default, this will be NULL.

Timeout

Specify the time duration (in seconds) beyond which this test should time out in the Timeout text box. The default is 10 seconds.

Detailed Diagnosis

To make diagnosis more efficient and accurate, the eG Enterprise suite embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option.

The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled:

  • The eG manager license should allow the detailed diagnosis capability
  • Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

State

Indicates current status of this IP address.

 

The numeric values that correspond to each of the above-mentioned values are as follows:

Measure Value Numeric Value
Dead 20
Bad 40
Reply_pending 60
Ready_inactive 80
Ready_active 100

Note:

By default, this measure reports one of the Measure Values listed in the table above to indicate the current status of the IP address. The graph of this measure however, represents the same using the numeric equivalents alone.

The detailed diagnosis of this measure shows the Mac address of each IP address. In addition, the number of interfaces bound to each IP address and the VLAN details are also revealed.

Reply age

Indicates the time duration taken by this IP address to receive a response via the ARP protocol.

Seconds

A sudden/gradual increase in the value of this measure may indicate the slowdown in the network, which may lead to network congestion.