I have a Sonicwall with two WAN connections, a primary WAN (X1) and backup WAN (X2). I have defined a DMZ on X3 in transparent mode, to use some of the public IPs from the WAN. I can't use NAT since these are VOIP servers, which are allergic to NAT. I am noticing that I can only specify the IP range from the primary WAN. If the primary WAN is down, I can't use the backup WAN.

Despite having two WANs, I am not able to achieve network redundancy. How can I use public IPs from both WAN ranges in transparent mode? Is it possible at all?

  • Can you set up two DMZ ports (one for each WAN) to a switch with VLANs, then trunk them both to the servers? That would require the servers to support 802.1Q trunking. The servers would then have IP addresses from both WANs on each server.
    – Ron Maupin
    Commented Nov 23, 2015 at 9:51
  • I tried creating two DMZ like you said, but there is no way to link them to different WANs. When I specified the IP range from the second WAN in the second DMZ, it refused saying it is not in the WAN subnet of the first WAN.
    – Sharath
    Commented Nov 23, 2015 at 10:40
  • Even if you could configure the SonicWALL to allow you to do what you want it wouldn't work the way you want: each VoIP server would have to have the IP configuration of only one of the WANs -- it couldn't work on the other WAN when the 1st failed. Even if you gave the VoIP servers 2 IPs you can only have 1 active default gateway. If you can't place the VoIP server behind the router (NAT) then you likely need your own block of routable IPs which can be assigned to the VoIP servers and routed via either (both) of the ISPs. (unless you can configure the VoIP server to change IP config itself)
    – PSaul
    Commented Nov 23, 2015 at 22:53
  • The VOIP server is a SBC which can handle multiple WAN profiles. But if Sonicwall can't provide access to two WAN subnets, then I'll use two Sonicwalls.
    – Sharath
    Commented Nov 24, 2015 at 7:49
  • Have you played with consistent NAT? It's one of the option related to VoIP. Maybe it's a solution for you. The idea is that Sonicwall intercepts VoIP signalling and try to make it NAT-transparent. In my experience, some deployments works really nice with this option enabled.
    – KorXo
    Commented Nov 24, 2015 at 13:21

2 Answers 2


Looks like there is no way to do it using single Sonicwall. Therefore, I will use two sonicwalls in parallel.

  • You should accept your answer do that the question doesn't keep coming back, looking for an answer.
    – Ron Maupin
    Commented Nov 24, 2015 at 7:55
  • I tried already, I can't accept my own answer until tomorrow. Looks like a forum restriction.
    – Sharath
    Commented Nov 24, 2015 at 8:54

Configuring Multiple WAN Subnets Using Static ARP with SonicOS Enhanced (SW3726) https://support.software.dell.com/kb/sw3726

  • Link-only answers are no good. You should edit the answer to include the relevant portions.
    – Ron Maupin
    Commented Mar 10, 2016 at 18:32
  • The link doesn't even work.
    – Sharath
    Commented May 11, 2016 at 11:51

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