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6.7.2 CELLULAR FAILOVER
In this mode, a dial-out cellular connection is only established if the main network is disrupted. The cellular connection normally
remains idle and in a low power state. It is only activated if there is a ping failure. This standby mode suits remote sites with
expensive power or high cellular traffic costs.
In this mode, the appliance continually pings nominated probe addresses over the main network connection. If there is
a ping failure, it dials out and sets up a dial-out ppp connection over the cellular modem and access is switched transparently to
this network connection. Then when the main network connection is restored, access is switched back.
Once you have configured the carrier connection, the cellular modem can be configured for failover.
This will tell the cellular connection to remain idle in a low power state. If the primary and secondary probe addresses are not
available, it will bring up the cellular connection and connect back to the cellular carrier.
FIGURE 6-16.
Navigate to System > IP.
Select Internal Cellular Modem (cellmodem01) from the Failover Interface pop-up menu.
Enter the Primary Probe Address and the Secondary Probe Address.
These are the two sites the console server pings to determine if the principal network is operational.
If the principal network fails, the cellular network connection is activated as the access path to the console server and any
managed devices.
NOTE: Only HTTPS and SSH access are enabled on the failover connection. This allows an administrator to connect to the console
server to diagnose and correct the network failure without offering third-parties a large attack surface.
As of firmware v3.1.0, the advanced console server supports automatic failure-recovery back to the original state before failover
by default.
The advanced console server continually pings probe addresses while in original and failover states. The original state will
automatically be set as a priority and re-established following three successful pings of the probe addresses during failover.
The failover state will be removed once the original state has been re-established.
For earlier firmware, which does not support automatic failure-recovery, to restore networking to a recovered state you need to run
the following command:
rm -f /var/run/*-failed-over && config -r ipconfig
If required, you can run a custom bash script when the device fails over. You can use this script to implement automatic failure
recovery, depending on your network setup. The script to create is:
/etc/config/scripts/interface-failover-alert
To check the connection status:
Navigate to Status > Statistics.
Click the Failover & Out-of-Band tab.
CHAPTER 6: FIREWALL, FAILOVER AND OOB ACCESS
