Ethernet Redundancy via Smart Probe

Owned by Kelli Higdon
Last updated: Mar 06, 2024
4 min read

Ethernet Link Redundancy via Smart-Probing enhances the 2020 SBC’s ability to initiate a switchover due to a failure in the network. Currently the IMG 2020 employs a link based Ethernet Redundancy scheme. In the current scheme, the IMG 2020 would initiate a switch-over such as from interface Data A0 to Data A1 located on the rear of the system. With the addition of this feature the IMG 2020 can be configured to employ a probe-based detection scheme. In this scheme, the IMG 2020 would probe a set of pre-configured endpoints (send an ARP request packet). The endpoints would then reply with a Gratuitous ARP packet. These packets inform the IMG 2020 that the endpoints are still alive. If the IMG 2020 sends out an ARP Request Packet and does not receive a Gratuitous ARP in return it will continue to send ARP Requests until the pre-configured number of requests is met. If at that time no Gratuitous ARP’s are sent back then a switchover to its Hot Standby Port (Data A1 in this case) will be initiated. If the switchover solves the problem, then calls will continue to be processed on the new switched-over port. However, if the issue is not solved, the IMG 2020 would continue to switch back and forth between Data A0 and Data A1 (ping pong effect) until the issue in the network is solved. The feature is enabled through the Web GUI and can be enabled on any of the network interfaces (CTRL, Data A, Data B).

If multiple endpoints are configured, the switchover will not occur unless ALL endpoints fail to respond to the ARP.

The second part of this feature allows the customer to initiate a link switchover manually. A manual switchover can be executed from the Logical Interface object within the Web GUI. The manual switchover was added to allow a customer the ability to switch from one network to another. An Event such as maintenance to a specific network is now possible by switching away from the network that needs maintenance to a different network that could handle any traffic while maintenance is being performed. Below is diagram displaying the Smart-Probing Via Ethernet Redundancy feature using ports Data A0 and Data A1.

Configuration

The procedure below displays the steps involved in configuring the Ethernet Redundancy Via Smart-Probe feature. The procedure uses Data A0 and Data A1 as the interfaces used for the Ethernet Redundancy feature. Data A0 will be the active port and Data A1 will be configured as the Hot Standby (Link is Up but Tx/Rx are disabled). The configuration below assumes the physical node or nodes have already previously been created and configured.

  • Right click on the IMG 2020:Node object and select New Network. An IP Network object pane will appear. No configuration is needed here. The IP Network object is a parent or container object and no configuration is required here. Refer to the IP Network Interface topic for more information on this object.

  • Right click on the IP Network object and select New Logical Interfaces. Under the Logical Interfaces object, multiple Logical Interface objects can be created. The Logical Interface object is a parent or container object and no configuration is required. Refer to the Logical Interfaces topic for more information on this object.

  • Right click on the Logical Interfaces object and select New Logical Interface. Select which interface (Control, Data A, or Data B) will be configured by selecting the interface from the drop down menu of the Interface field. This will be the interface that the Smart Probe feature will be configured on. Refer to the Logical Interface topic for more information on this object.

  • Right click on the Logical Interface object and select New Smart Probe Detection. Refer to the screen capture and information below.

 

 

Probe Detection (Default = Disabled)- To enable the Smart Probing feature on the interface selected in step 3, select Enabled from drop down list.

Probe Interval – Select from drop down menu number of seconds to wait between sending a second, third, and so forth ARP request to the external VoIP entity.

Probe Threshold – Select from drop down menu the number ARP requests that will be sent before initiating a switchover from the primary to the secondary interface.

Refer to the topic for more information on this object.

  • Right click on the Smart Probe Detection object and select New Smart Probe Endpoint. This object will configure the VoIP entity that the interface configured above will communicate with. The Smart Probe feature is supported when utilizing IPv4 only so IPv4 will be the only selection in the Address Type field.

  • In the IP Address field, enter the IP address of the endpoint that the IMG 2020 will send the ARP request packets to.

Additional Information

  • Ethernet Redundancy via Smart Probing is configurable on all three network interfaces (Control 0/1, Data A0/A1 and Data B0/B1), located on rear of IMG 2020.

  • A probe packet is not confined to any one subnet. As long as there is a valid IP address, the IMG 2020 can send a probe message to it.

  • A probe message is an ARP request.

  • If the Hardware address is known for an endpoint then a unicast ARP packet rather than a broadcast packet will be sent.

  • The receipt of a Gratuitous ARP from an endpoint will cause the cached HW address to be updated.

  • A switchover will generate gratuitous ARPs over the newly active port.

  • A switchover will flush the Hardware address of each endpoint from the ARP Cache.

  • A switchover will reset the missed probe count.

  • Changing configuration information will result in probe logic being reset. Any missed probe counts will be reset.

  • Minimum interval at which probe packets can be sent is 1 second.

  • Minimum time between switch-overs is 10 seconds.  

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