Enabling the cellular watchdog is recommended for long running cellular connections that may be regularly idle, particularly Always-on OOB, Dormant Failover OOB and IP Passthrough modes.
When a cellular connection is idle for long periods of time, or when a cell tower is particularly busy, the carrier may silently drop the Opengear device's data connection. From the Opengear device's perspective, the only way to determine whether a drop out has occurred is to proactively probe data connectivity using ICMP ping.
The pings themselves act as a keepalive to help maintain connectivity. If connectivity should be lost, the Opengear device reboots to force a clean restart of all connection processes and its integrated cellular module.
Note that the watchdog will trigger whenever the ping test conditions fail, so will also be triggered e.g. by SIM/account credit running out.
1. Log into the Opegear appliance Web UI. First time setup instructions can be found in the Quick Start Guide.
2. Configure your cellular connection as per usual. Before applying, scroll down to the Modem Watchdog section:
- Check Enable watchdog
- Enter a reliable Address that will respond to pings, e.g. 18.104.22.168
- Enter a Threshold of consecutive failed test runs after which a reboot will trigger
- Enter the Ping count to send per test run
- A small value such as 3 is sufficient in most cases
- Note that a test run is considered passed only when all ping responses succeed
- Enter the Period in seconds to wait between test runs
- T-Mobile recommends using 1680 seconds (28 minutes)
It is important to tune these values to ensure you are not generating too much traffic for your data plan.
With the default settings, 5 x 64 byte pings are sent every 30 seconds. The ping responses will typically also count as metered data. Assuming this, the default setup will generate about 50MB monthly on top of normal data usage.
For example, reducing Ping count to 3 and increasing Period to 120 seconds or greater reduces data to under 10MB monthly.
Finally, set the Threshold to balance false positives against acceptable outage time before automatic recovery is triggered.
20 minute safety net
If after a connection is successfully established then dropped, a subsequent successful connection to the carrier cannot be established within 20 minutes for whatever reason, automatic recovery is triggered.
Here's an example that will perform a ping test to Google DNS every 181 seconds and when 10 consecutive test run fails, the unit will reboot.
config -s config.cellmodem.watchdog.enabled=on
config -s config.cellmodem.watchdog.probe=22.214.171.124 config -s config.cellmodem.watchdog.threshold=10 config -s config.cellmodem.watchdog.count=3 config -s config.cellmodem.watchdog.period=181 config -r dialin
Note: T-Mobile recommends watchdog.period=1680
Web UI example from ACM7004-5-L
In "System" section, click "Dial"
Scroll down to the Modem Watchdog section, click "Enable watchdog" box, and complete fields. Then click "Apply Modem Dial Settings".