Interfaces WideArea Networks(WANs)
IX20 User Guide
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Configure SureLink active recovery to detect WAN/WWAN failures
Problemscan occur beyond the immediate WAN/WWAN connection that prevent some IPtraffic from
reaching its destination. Normally this kind of problem doesnot cause the IX20 device to detect that
the WAN hasfailed, because the connection continuesto work while the core problem exists
somewhere else in the network.
Using Digi SureLink, you can configure the IX20 device to regularly probe connectionsthrough the
WAN to determine if the WAN hasfailed, and to perform recovery actions, such as changing the
interface metric to use a new default gateway.
Required configuration items
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Enable SureLink.
By default, SureLink isenabled for the preconfigured WAN (ETH1) and WWAN (Modem). The
default configuration tests the DNSservers configured for the interface.
When SureLink is configured for Wireless WANs, SureLink tests are only run if the cellular
modem is connected and hasan IPaddress. Use the SIM failover optionsto configure the IX20
device to automatically recover the modem in the event that it cannot obtain an IPaddress.
See Configure a Wireless Wide Area Network (WWAN) for details about SIM failover.
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The type of tests to beperformed:
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Ping test: Uses ICMPto determine connectivity. The default behavior isto ping the
interface gateway, which meansthat an initial traceroute issent to the hostname or IP
addressconfigured in the SureLink advanced settings, and then the first hop in that route
isused for the ping test.
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DNS test: Performsa DNSquery to the named DNSserver.
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HTTP test: UsesHTTP(s) GETrequests to determine connectivity to the configured web
server.
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Test DNS servers configured for thisinterface: Tests communication with DNSservers
that are either provided by DHCP, or statically configured for this interface.
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Test the interface status: Tests the current statusof the interface. Thetest fails if the
interface is down. Failing thistest infers that all other testsfail.
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Custom test: Teststhe interface with custom commands.
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TCP connection test: Tests that the interface can reach a destination port on the
configured host.
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Test another interface's status: Tests the statusof another interface.
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The actionsto 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.
This recovery action is enabled by default for the preconfigured WAN and WWAN interfaces.
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Restart interfaceThis recovery action is enabled by default for the preconfigured WAN and
WWAN interfaces.
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Reset modem: This recovery action is enabled by default for the preconfigured WWAN
interface.
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Switch to alternate SIM: Switches to an alternate SIM. Thisrecovery action is enabled by
default for the preconfigured WWAN interface.
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Reboot device.
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Execute custom Recovery commands.
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