Digi WAN 3G User Manual page 106

Link integrity monitoring settings
 Enable Link Integrity Monitoring using the test method selected below: Enables or
disables the link integrity monitoring tests. If this setting is enabled, the other Link
Integrity Monitoring settings may be configured and are used to verify the functional
integrity of the mobile connection. The default is off (disabled).
There are three tests available:
– Ping Test
– TCP Connection Test
– DNS Lookup Test
You can use these tests to demonstrate that two-way communication is working over the
mobile connection. Several tests are provided because different mobile networks or
firewalls may allow or block Internet packets for various services. Select the appropriate
test may be selected according to mobile network constraints and your preferences.
The link integrity tests are performed only while the mobile connection is established. If
the mobile connection is disconnected, the link integrity tests are suspended until the
connection is established again.
For the link integrity tests to provide meaningful results, the remote or target hosts must
be accessible over the mobile connection and not through the LAN interface of the
device (if it has one). That is, the settings should be configured to guarantee that the
mobile connection is actually being tested.
The link integrity test settings may be modified at any time. The changes are used at the
start of the next test interval.
 Ping Test: Enables or disables the use of "ping" (ICMP) as a test to verify the integrity
of the mobile connection. The test is successful if a valid ping reply is received in
response to the ping request sent. The ping test actually sends up to three ping requests,
at three second intervals, to test the link. When a valid reply is received, the test
completes successfully and immediately. If a reply is received for the first request sent,
there is no need to send the other two requests.
Two destination hosts may be configured for this test. If the first host fails to reply to all
three ping requests, the same test is attempted to the second host. If neither host replies
to any of the ping requests sent, the test fails. The primary and secondary addresses may
be either IP addresses or fully qualified domain names.
– Primary Address: First host to test.
– Secondary Address: Second host to test (if the first host fails).
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