Digi Connect WAN Series User Manual page 88

Digi Connect WAN Family web interface
DNS Lookup Test: Enables or disables the ability to use a Domain Name Server (DNS) lookup
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as a test to verify the integrity of the mobile connection. The test is successful if a valid reply is
received from a DNS server. Typically, this means the hostname is successfully "resolved" to an
IP address by a DNS server. But even a reply such as "not found" or "name does not exist" is
acceptable as a successful test result, since that demonstrates successful two-way
communication over the mobile connection. When a valid reply is received, the test completes
successfully and immediately.
The DNS servers used in this test for the hostname lookup, are the primary and secondary DNS
servers obtained from the mobile network when the mobile PPP connection is first
established. You can view these addresses by going to Administration > System Information
> Mobile.
Note that this DNS test is independent of the normal DNS client configuration and lookup
cache, which is used for other hostname lookups. This test specifically requires communication
over the mobile connection for each lookup, and to avoid being "short-circuited" by previously
cached information. Also, this test does not interfere in any way with the normal DNS client
configuration of this device.
Two hostnames may be configured for this test. If the first hostname fails to get a reply, the
same test is attempted for the second hostname. If no reply is received for either hostname,
the test fails. The primary and secondary DNS names must be fully qualified domain names.
Note that the reverse lookup of an IP address is possible, but that is usually unlikely to succeed
in returning a name. Still, you can use a reverse lookup to demonstrate the integrity of the
mobile connection.
Primary DNS Name: The first hostname to look up.
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Secondary DNS Name: The second hostname to look up (if the first hostname fails).
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Repeat the selected link integrity test every N seconds: Specifies the interval, in seconds,
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at which the selected test is initiated (repeated). A new test will be started every N seconds
while the mobile connection is established. This value must be between 10 and 65535. The
default is 240.
If the configured interval is less time than it takes a test to complete, the next test will not be
initiated until the previous (current) test has completed.
Test only when idle: Initiate the selected link integrity test only after no data has been
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received for the specified interval of time. This changes the behavior of the test in that the test
interval varies according to the presence of other data received from the mobile connection.
Although using this idle option may result in less data exchanged over the mobile connection, it
also prevents the link integrity tests from running as often to verify the true bi-directional
state of that connection.
Digi Connect WAN Family User Guide
Configuration through the web interface
88