LTE Failover

Topic

This article describes the LTE failover feature on the Datto Networking Appliance (DNA).

Environment

  • Datto Networking Appliance (DNA)

Description

The Datto Networking Appliance can automatically fail over to a 4G LTE cellular network in the event of a WAN interruption. The appliance will automatically switch into failover mode if it meets one of the following conditions:

  • The DNA loses the physical link to it's WAN port.

  • The appliance is unable to reach the DNA check-in servers.

  • The appliance loses connection to its OpenDNS and Google DNS servers for 15 consecutive seconds.

The carrier to which it fails over varies by region. See our Datto Networking Appliance (DNA): Region And Hardware Specifications article for more information about service provider regions and availability.

All devices dependent on an Internet connection will continue to function as usual. You may also notice a marginal decrease in connection speed due to cellular bandwidth limitations.

When the DNA detects restored connectivity on its WAN port, it will exit failover mode and resume regular operation. You will not need to reset the connection manually.

Acceptable use

LTE Failover is reserved for emergency business continuity situations involving an outage with the primary ISP. Failover exceeding ten days or 50 GB of usage in a 30-day period or more than a total of 30 days in a 365-day period is considered outside current usage guidelines and is subject to limited LTE service.

  • LTE Failover can only be used during temporary periods of primary internet service failure. LTE is not a long-term substitute for primary internet service.
  • LTE Failover may not be used in a manner that results in excessive data use over the LTE network.
  • Certain device features may work in an altered or degraded state while the appliance is in LTE Failover.
  • Some applications, such as those which rely on streaming video, may not be accessible during LTE Failover.

For full details about Datto's LTE usage policies, refer to the Datto Networking Product Terms of Use (requires Datto Partner Portal login).

Functionality changes during LTE Failover

During LTE Failover, the following functionality changes occur:

  • The LTE modem will receive an IP address, but any provided DDNS names will not work while the device is in failover.
  • Port forwarding is non-functional.
  • IPsec functionality changes in the following ways:
    • If the DNA is the initiator and it goes into failover, the tunnel will still work.
    • On DNA-to-DNA IPsec connections, if the responder enters failover mode, but the initiator still has a WAN connection to the ISP, the DNA will change the responder to the initiator tunnel will work.
    • If both units in a DNA-to-DNA connection are in failover, IPSec will not work.
  • ClientVPN users will be unable to connect due to carrier-grade NAT preventing uninitiated inbound connections. This case applies to both IKEv2 and OpenVPN.

Testing Failover Mode

The DNA's Test Failover option allows you to simulate a network interruption to evaluate the device's performance in 4G LTE mode.

Testing cellular failover will temporarily shut down the DNA's WAN connections, interrupt existing network connections, and activate the device's cellular failover functionality. Your network will function in a degraded state while the failover test runs. Use caution when testing this feature in a production environment.

To access the LTE/4G Failover UI, log into the DNA web interface, and click Status.

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The WAN Details card is on the right-hand side of the page. Click the Test Failover button in the LTE/4G Failover category to begin the test.

While the test runs, the DNA will display the banner shown below. The test can take up to a minute to complete.

The DNA will return to the WAN connection on its own after the test finishes.

If no cellular service is available

If the modem cannot find cellular service, the UI will display the status message shown below.
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