I'm writing because i have a very strange issue with a newly installed debian 9.5 server. This server is behind a NAT made with a SonicWall firewall that assigns a public dedicated address to this server.

The internal IP address of the debian server is and the firewall NATs this IP address to 93.xx.xx.220, but I see that the server's IP address gets translated to the default address (93.xx.xx.196) instead. So I assigned the private IP address to another machine and this successfully gets translated to 93.xx.xx.220 on the firewall.

I've checked for env variables like http_proxy, https_proxy, checked for some kind of iptables rule that redirects traffic to the internal proxy, but I've found nothing. Does anyone have other suggestions on what can i check? Thanks in advance

  • 1
    pcaps and full configs are probably going to be the first step.
    – womble
    Oct 16, 2018 at 10:29
  • did you use the Sonicwall wizard to set up the NATting rules etc? Or manually? Can you share the details of the NAT rules?
    – Phil
    Oct 16, 2018 at 11:41
  • Yes i've used the public server wizard
    – Tiziano
    Oct 16, 2018 at 11:47

1 Answer 1


Make sure your server is in the correct SonicWall Zone/Port.

Outbound NAT rule are evaluated on the source IP and the source zone too. Thus your other server must match all the condition for the outbound NAT rule to correctly apply.

  • Thanks for the info. I'm digging deeply and i saw that some sites, like whatismyip.com and dnsstuff.com sees the correct address, others instead sees the wrong one, so i think that it's a firewall issue
    – Tiziano
    Oct 16, 2018 at 13:45
  • @Tiziano whatismyip see your outgooing IP, so your router is ok now, but dnsstuff see DNS's entry IP, we mix two thing now, it's not the same thing
    – yagmoth555
    Oct 16, 2018 at 13:47
  • dnsstuff sees the correct address... i get the wrong address by using for example user@sdiws:~$ curl http://checkip.amazonaws.com/ 93.xx.xx.196
    – Tiziano
    Oct 17, 2018 at 15:31

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