Link Control device ("pingovalka")

    The article describes its own development - a device for monitoring the condition of the link and equipment. The idea of ​​the device is not new, the point is to periodically send ICMP requests to the specified addresses and the subsequent reaction in case of not receiving a response.
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    general description



    The device is designed to control the IP connection with devices on the network and can be used to control the availability of a network node or outgoing connection outside the network.

    The device is equipped with an interface for connecting to an Ethernet network, a relay output with a normally closed contact for connecting power circuits or control circuits of controlled equipment, as well as a power connector for the device itself.

    Relay output allows switching circuits with voltage up to 250 volts and current up to 10 amperes.
    The power supply voltage of the device is 5V. Current consumption up to 100 mA.

    Typical device connection schemes



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    In this scheme, the Link Control device is connected in the local segment of the monitored equipment and checks the availability of a specific node in the external segment. The device controls the channel between the router and the provider's network, and if the connection is lost, Link Control will reboot the router through the power supply.

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    In this scheme, the availability of a certain node in the network is controlled and, in the absence of connectivity with the equipment, the Link Control device will reboot the node through the power supply or reset circuits.

    Device configuration


    The device is configured using the Link Control Configuration software . To configure the device, SNMP is used; to connect to the device, you must specify the IP address of the device and the Community String used.

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    To restore the initial settings, you must press the Reset button located inside the device for 5 seconds, the hole for accessing the button is located on the top cover of the device.

    To change the settings in the corresponding fields of the configurator, you must specify the current address and community, after which the program will receive all current settings from the device or display an error message if any of the parameters is entered incorrectly.

    Device settings are defined in four tabs of the program, in the “Network” tab, the current network settings are configured, as well as the Community String parameter. Changes are sent to the device after clicking the “Apply” button opposite the corresponding field.

    If you change the address of the device or community, you must reconnect to the device and get the current settings.

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    In the "Description" tab, you can configure the name of the monitored device, its short description and geographical location, all of these fields are standard for the SNMP protocol.

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    In the “Link Control” tab, the device’s behavior when controlling equipment via ICMP is configured. ICMP interval
    fielddetermines how often ICMP requests are sent to the specified IP addresses, the value of the field is indicated in seconds.
    The Wait Interval field determines the time the device waits between the operation of the relay output and the start of sending ICMP requests. It can be adjusted to adapt to the operating system boot time in controlled nodes.
    The First IP address field determines the primary address to which ICMP requests will be sent.
    The First threshold field determines how many unacknowledged requests will be sent before the relay output trips.
    Field Second IP Addressdefines a secondary control address to which requests will be sent when the first threshold of unconfirmed packets is reached.
    The Second Threshold field determines how many unacknowledged requests will be sent before the relay output trips.
    The Use first IP address and Use second IP address fields determine whether the device will send requests to the specified addresses.
    The second address can only be used if the first address is used. Receiving a response to a request at any of the addresses resets the threshold values ​​of both addresses.

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    The “SNMP-Trap" tab defines the settings for sending notifications when a relay is triggered. Monitor Address fielddetermines the IP address of the control station to which notifications of the relay output are transmitted. The parameters defined in the Description tab are passed to SNMP-Trap.
    Optionally, you can enable or disable the sending of SNMP-Trap notifications when a relay is triggered.
    The “SNMP-Trap" tab also has a button that allows you to force the relay output for testing.

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