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Setting up secondary WAN with same subnet?

I have 2 WAN Connections for my facility. Both have static IP Addresses (Example: & These static addresses are provided to me by the ISP. I have the two WAN Connections coming into the SonicWALL, one as the primary and the secondary. Each WAN connection comes into my facility via different route for redundancy but make it back to the same router at the ISP. 

The question is, since both addresses are on the same subnet, how can I add them both to the SonicWALL. When I try to setup the secondary connection it gives me the error (Error: Subnet on the interface overlaps with another interface). Any idea's on how I can make this work?

From what I was told the original setup for this facility was that there were two different circuits for the building. two 50mb connections and one was used for business purposes and one was used for guest services. The old administrator simply had two networks split and one was for guests and one for business. I've combined both so they could both be monitored by the firewall and that's where I'm running into this problem. The reason I need this to work is so I can have monitoring of the static IP. I forward all DNS requests to a government entity that watches the traffic to determine if people are accessing malicious sites and I receive a report every month. Since the SonicWALL has the two different connections, sometimes it uses the static address and then sometimes it uses DHCP because the two WAN connections are coming into the firewall. I just want all traffic coming out of the firewall to be on one of the two static addresses so they can be monitored. 


Category: Entry Level Firewalls


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    AjishlalAjishlal Community Legend ✭✭✭✭✭


    Install a WAN switch in front of the Sonicwall and connect the two ISP connections from the same subnet.

    On Sonicwall, assign a WAN IP from the same subnet & setup two outbound routes for each link.

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    SliderhomeSliderhome Enthusiast ✭✭
    edited September 2021


    I tested a time ago:

    The sonicwall has no problem with 2 ISP's with the same subnet's (internal 192.168.2.x DHCP) on different wan ports.

    Add a second WAN example on x2 and connect the second ISP to that interface

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    @Sliderhome and @Ajishlal thank you for the replies.

    @Sliderhome I've attached an image of my interfaces with the information changed. But for example,

    My primary WAN connection coming into my facility has an external static IP assigned to ( In the picture it is labeled as the secondary WAN. My ISP has provided me with a second connection that comes into my facility and the static IP for it is ( When I try to enter as the static address for the secondary Default WAN it get a conflict telling me the two WAN connections can't be on the same subnet.

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    SliderhomeSliderhome Enthusiast ✭✭


    I tested with same subnet received form DHCP it works fine.

    If you have 2 internet connections with and .2 are you sure the subnet is ?

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    @Sliderhome Those IPs were incorrect. The ISP provided me with the IP Addresses I use and the subnets. When I input them both I get that error message (Error: Subnet on the interface overlaps with another interface). I'm thinking of asking the ISP to change one of the subnets to something like IP1 and IP2 so that the SonicWALL will let me enter it. I wish I could bridge the two WAN connections and use one IP but I don't think that's possible.

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    andyoeftandyoeft Newbie ✭
    edited May 2023

    Unfortunately it appears no one on this thread has the actual answer to this problem. I've accomplished exactly what is described here By @Twizz728 using EARLIER versions of Sonicwall TZ routers (SOHO and 300) but the TZ270 refuses to cooperate. This error would make sense IF the interfaces being created were LAN interfaces, not WAN interfaces. If anyone here has found the actual solution that would be appreciated. On hold now with SW. Hopefully someone picks up the phone.

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    Twizz728Twizz728 Newbie ✭
    @andyoeft I was never able to get a clear resolution on this. I tried the examples above but nothing ever worked correctly. I ended up creating a guest network with the secondary WAN circuit without the sonicwall being used. Socks that I had to do that.
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    @andyoeft I'm still researching this issue. If you found a way please let me know, but I believe the only solution currently is to do what @Ajishlal mentioned above and that was to Install a WAN switch in front of the Sonicwall and connect the two ISP connections from the same subnet, then on the Sonicwall, assign a static WAN IP from the same subnet & setup two outbound routes for each link.

    I've decided to no longer load balance my WAN connections so I'm planning on have WAN1 go to LAN1 and WAN2 go to LAN2. I want both to have a public static IP and unfortunately I can add both to the SonicWALL since they are on the ISPs same subnet. What I plan on doing is setting up a WAN switch for my LAN2. I will have the WAN2 circuit to come into the WAN switch where the public static IP would be assigned and then from the WAN switch I will create a WAN interface on the SonicWALL (WAN2) and set it to DHCP. So what I assume will happen is the traffic leaving the WAN2 interface on the SonicWALL would leave DHCP and once the traffic hit the WAN switch it would then go out over static IP and have the static IP address.

    I hope I said all that right.

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