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TZ400 in high availbilty mode with 4G USB adapter


I have 2x TZ400 firewalls running in high availbility mode. The firewalls are behind a cisco C881 service router from our internet provider.

I woud like to install a 4G USB adapter for internet backup purposes. The 4G adapter is DWM222 from d-link and supported by sonicwall. But the 4G adapter makes no connection. I have tried different connection settings but no luck.

I had the 4G adapter connected to the sonicwall for serveral hours but suddenly the sonicwall could not ping to the cisco router anymore. No internet was availabe since then. I removed the 4G adapter and restarted the sonicwall and cisco router and everything was up again.

Is it possible to use a 4G adapter in combination with a high availbilty setup? Has anyone experience with this?

Why is the 4G adapter not working? I know the adapter is OK because I have test it on another devices.

Category: Entry Level Firewalls


  • TKWITSTKWITS Community Legend ✭✭✭✭✭

    I'd say you'd need two cellular adapters for a true HA setup.

    I'm speculating, but what likely happened when you lost connectivity was HA decided to failover to the device without the cellular connection. Since that device had settings assuming the cellular was there but didn't, it caused the routing to get borked.

  • Hello @Reinder,

    Welcome to the SonicWall community.

    Unfortunately, the 4G USB adapters are not compatible with HA. Since it can be either plugged into the primary or secondary device. The network set up needs to be identical when set up in HA.


    Shipra Sahu

    Technical Support Advisor, Premier Services

  • TKWITSTKWITS Community Legend ✭✭✭✭✭

    @shiprasahu93 For clarification, even if you had two 4G USB adapters (one for each primary and secondary unit) HA wouldn't function properly??

    I would think this would be an accepted configuration.

  • ReinderReinder Newbie ✭


    I have only 1 4G adapter. But I cannot get this adapter to work.

    What would be the best solution for an internet backup?

  • AjishlalAjishlal Community Legend ✭✭✭✭✭

    Hi @Reinder

    Instead using the 4G USB modem, I would recommend to use the 4G LTE normal modem and insert your SIM.

    Then configure your 4G modem LAN interface for the Sonicwall primary & HA unit. So in this scenario you would get fail-over connection as well as it will support HA.

  • ReinderReinder Newbie ✭
  • ReinderReinder Newbie ✭


    Can you maybe expain how to set this up with a TZ400 sonicwall?

    The sonicwall is connected to internet with WAN interface. I would like to keep it this way.

  • AjishlalAjishlal Community Legend ✭✭✭✭✭

    Hi @Reinder

    You have to configure one more additional WAN interface in your sonicwall and connect to the 4G modem LAN1 port & LAN2 connect to the HA unit.

  • TKWITSTKWITS Community Legend ✭✭✭✭✭
    edited June 2021

    This wouldn't be true HA since you are relying on a single 4G modem and SIM card... If someone at Sonicwall could confirm or deny using two 4G USB adapters would be accepted we could know for sure! @shiprasahu93 @Micah @Saravanan

  • ReinderReinder Newbie ✭


    We are have a working HA setup with 2x TZ400. But we would like to have a backup when our main internet connection goes down.

    The backup connection will be a 4G connection. Is this possible with a HA setup?

    Can you advise how to do this?

  • CharizardCharizard Newbie ✭
    edited September 2022

    With HA you need to have the exact same connections on both devices.

    If it worked for one, logically you should be able to plug in a Y-cable to both USB ports or a powered USB hub that is capable of powering your USB modem and connect both Sonicwall members to the same USB modem. I just don't know if the Sonicwalls provide enough milliamperes to drive the 4 modem.

    Did you test uploading-downloading real life data volumes, or just a basic ping test?

    4G modems are power hungry and might pass a few pings but then might die when trying to do real work.

    Try a powered USB hub. Both to power the 4G and to connect both Sonicwall units in the event of a failover. Or combine it with a USB y-cable and power brick.

    Are you running a long USB cable to bring the 4G close to a window for good reception? Long runs can impact low-voltage DC power transmission.

    Did the 4G reconnect when you failed it back over to the correct unit?

    Unlike the wired connections the 4G is not always-on. I remember it needing a trigger to connect. Do you have logical monitoring enabled on the other line? So it can trigger the 4G to connect?

    To test, simulate a real-life ISP outage by disconnecting upstream from the wan port (e.g. disconnect the coax on a cable modem), so the sonicwall interface is still up. Then see if the ISP failover does what you want it to do. Once you establish that, test combinations with individual HA unit failures.

    If you are not using an unlimited wireless plan, or have a throughput cap, and the wireless vendor allows, add e-mail alerts with the vendor when you hit different percentages of data volume. Just for sanity in case it fails over and starves the data plan. This way you can call the wireless provider and bump up the plan. Or know if it did not fail back when expected.

  • ArkwrightArkwright All-Knowing Sage ✭✭✭✭

    If you have two USB 4G and 2x SIMs then you're paying for 2x SIM rentals, which seems a bit wasteful for a backup-of-a-backup WAN.

    A vote for 4G ethernet router here.

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