Digi 90000566_H manual Dns, Trigger=intervalidle, Interval

set surelink

dns

DNS Lookup Test. This test uses a Domain Name Server (DNS) lookup 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. These addresses may be viewed in your web browser on the Administration System Information Mobile page.

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 has been specifically designed to require 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 should 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, such a reverse lookup can be used to demonstrate the integrity of the mobile connection.

trigger={intervalidle}

The conditions under which link integrity monitoring tests are performed.

interval

Link integrity monitoring tests are repeated at the interval specified by the “interval” option.

idle

Link integrity monitoring tests are performed only when idle; that is, if no data is received for the period of time specified by the “interval” option.

This value 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 "trigger=idle" may result in less data being 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.

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