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Interfaces
Configure SureLink active recovery to detect WAN/WWAN failures
Problems can occur beyond the immediate WAN/WWAN connection that prevent some IP traffic from
reaching its destination. Normally this kind of problem does not cause the Connect IT 4 device to
detect that the WAN has failed, because the connection continues to work while the core problem
exists somewhere else in the network.
Using Digi SureLink, you can configure the Connect IT 4 device to regularly probe connections through
the WAN to determine if the WAN has failed, and to perform recovery actions, such as changing the
interface metric to use a new default gateway.
Required configuration items
Enable SureLink.
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By default, SureLink is enabled for the preconfigured WAN (WAN) and WWAN (Modem). The
default configuration tests the DNS servers configured for the interface.
When SureLink is configured for Wireless WANs, SureLink tests are only run if the cellular
modem is connected and has an IP address. Use the SIM failover options to configure the
Connect IT 4 device to automatically recover the modem in the event that it cannot obtain an
IP address. See
failover.
The type of tests to be performed:
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Ping test: Uses ICMP to determine connectivity. The default behavior is to ping the
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interface gateway, which means that an initial traceroute is sent to the hostname or IP
address configured in the SureLink advanced settings, and then the first hop in that route
is used for the ping test.
DNS test: Performs a DNS query to the named DNS server.
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HTTP test: Uses HTTP(s) GET requests to determine connectivity to the configured web
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server.
Test DNS servers configured for this interface: Tests communication with DNS servers
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that are either provided by DHCP, or statically configured for this interface.
Test the interface status: Tests the current status of the interface. The test fails if the
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interface is down. Failing this test infers that all other tests fail.
Custom test: Tests the interface with custom commands.
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TCP connection test: Tests that the interface can reach a destination port on the
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configured host.
Test another interface's status: Tests the status of another interface.
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The actions to take to recover connectivity in the event of failed tests:
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Change default gateway: Increases the interface's metric to change the default gateway.
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This recovery action is enabled by default for the preconfigured WAN and WWAN interfaces.
Restart interfaceThis recovery action is enabled by default for the preconfigured WAN and
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WWAN interfaces.
Reset modem: This recovery action is enabled by default for the preconfigured WWAN
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interface.
Switch to alternate SIM: Switches to an alternate SIM. This recovery action is enabled by
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default for the preconfigured WWAN interface.
Reboot device.
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Digi Connect IT® 4 User Guide
Configure a Wireless Wide Area Network (WWAN)
Wide Area Networks (WANs)
for details about SIM
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