RUT240 and Dynamic DNS WWAN0 failover

We deploy and manage a large fleet of RUT240 (RUT2XX_R_00.01.14.7) mainly with mobile only connections. However, we have some sites that also are configured
with wired WAN as a failover. We configure the RUT240 WAN to be fixed ip ( within the wired LAN (gateway range when it fails over. When the mobile (primary) connection fails it fails over to the wired WAN all works fine as I would expect!

However, it does not ever seem to run the regular dynamic DNS script, so the dynamic domain names does not get updated to the public ip of the wired WAN.
The work around for our team has been to respond to the email that we configured to be sent from the RUT240 advising a WAN failover, and then we manually update the dynamic domain name record (of the RUT240) to the WAN public address.

Perhaps this is a deliberate design on your firmware, but it is my guess that the RUT240 when it fails over to the WAN, the RUT240 considers its new WAN address is that set in WWAN0 interface rather than that retrieved via the checkip URL in the dynamic DNS configuration. The WWAN0 address in this case is a LAN (local IP eg ) on the wired LAN.
Further it is my guess that either the RUT240 does not attempt to update dyndotcom with a local address or dyndotcom does not accept local addresses for update.

To resolve this issue, and after receiving any advice from your team - I am considering:

installing a regular shell script in a cron job on the RUT240 (say every 10 minutes) to either

  1. check (dyndns check URL) and update as necessary directly using the dyndotcom api scripts and disable the dynamic DNS service package


  1. monitor WWAN0 and if it should update to a private LAN ip on the Wired WAN (fail over) then update the dynamic IP directly using the dyndotcom api scripts.

I would appreciate any further insights you can offer.



The firmware used on your devices is very outdated, thus I cannot provide the exact instructions for that release in particular.
However, on newest RutOS releases it is possible to select how the public IP of the device is determined:

  • Custom - IP address will be taken from the selected WAN interface;

  • Public - an API call will be used to determined what IP address is used to reach the internet;

The second option is the one that you’d need. Later on, interval can be configured on how often to check if the IP address has changed:

So in your case, updating the firmware is highly recommended, however, if that’s not possible, a crontab could be added to restart the DDNS service.

Best regards,

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