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TZ 350 behind an ISP modem

Client has TZ350 and setup new ISP. ISP modem router acting as firewall. I would like to setup the Sonicwall behind it.

Category: Entry Level Firewalls


  • Hi @JEDB,

    Thank you for visiting SonicWall Community.

    Could you please let us know if you are planning to insert the TZ 350 into an existing network? Or IP and subnet changes can be done?

    Please share your network diagram with IP subnetwork details for better suggestions.


    Saravanan V

    Technical Support Advisor - Premier Services

    Professional Services

  • jedbjedb Newbie ✭

    Hi Saravanan,

    I would place it behind the modem. I cant change the modem config and it has Wireless as well.

    Modem-> TZ350-> Switch.

    I would to be all on one LAN segment.


  • Hi @JEDB,

    I would suggest you to make use of layer 2 bridging concept on the TZ 350. Please refer the section Inline Layer 2 Bridge Mode on the below weblink. This would match your scenario.

    Configure the X1 interface on the same subnet as that of the ISP router and bridge the X0 interface with X1 interface using Layer 2.

    Please let me know if any questions.


    Saravanan V

    Technical Support Advisor - Premier Services

    Professional Services

  • AjishlalAjishlal Community Legend ✭✭✭✭✭

    Hi @jedb

    What you suggested above, as per the security prospective it's not recommended because your WiFi traffic is not passing through the Firewall and those users are not protected from the threats.

    So recommended to configure as same as below;

    Modem-->Firewall-->Switch-->WiFi AP

    For example; Change the Modem LAN IP and configure the same subnet in Firewall X1 interface and configure the old Modem Subnet (LAN) in X0 and connect the Switch and WiFi AP under the X0 interface. So in this scenario WiFi & Ethernet users will be in same subnet and both are under the Firewall protection.

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