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by anonymous
Hi  All,

I need to use the rutx12 as pure modem without any features. External fortigate firewall device will be responsible for handling routing and firewall.

For this we need to use both modems at the same time from RUTX12 and passthrough those to fortigate device as WAN1 and WAN2. And we will be able to use forigate SD-wan feature for load balance between these two connections.

Is it possible to passthrough both modes to external device? if yes  what are the steps

or Do I need to use NAT and separate VLAN for each modem ? - > we don't like this method as this will force the double nat and all the traffic will load balance within the rtux12 as well.


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by anonymous


Thank you for reaching out!

Unfortunately, passthrough mode is only available on a single modem.

There would be a few solutions to achieve this:

  • Using an RS cable for a complete modem passthrough;
    • While this would be possible using a USB hub, it would mean, that the Fortigate device would need to control the modems and transfer the data using AT commands. This would also limit the bandwidth quite a bit.
  • Using VLANs as mentioned before, but turning off NAT (only if the carrier can provide more than 1 IP address per SIM card);
    • To avoid double-NATing, separate firewall zones can be configured for each SIM with Masquerading flags disabled for both of them. This will disable NAT on the RUTX12.
    • In this case, however, SIM cards will need to have more than one public/private IP address, as the router will get its own IP address, as well as the FortiGate device.

I'd like to ask you for your topology, perhaps we'll be able to find another solution.

Best regards,