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DNAT and loopback issue - some IPs work but some don't

Hi everyone,

I am migrating my setup from Sophos UTM to Sophos Firewall XG and I've come across this strange issue with my config that I cannot figure out. Hopefully it shouldn't be a difficult one to track down. I've set-up a DNAT for port 22 and 993 (SSH and secure IMAP respectively) using the Server Access Assistant. The assistant also created the reflexive and loopback rules. I can access the IMAP server from outside just fine, no issues. As a background, the firewall has one static public IP and connections to port 993 are routed to the internal server. The internal network has multiple servers, say server 1 to 5. I can access the IMAP server from all the internal servers using the public IP apart from ONE specific server, let's call this server server 3.  For this one server I have another DNAT rule (including reflexive and loopback) for port 80 i.e. incoming connections to port 80 are routed to that server. All internal servers have access to port 80 via the public IP.

From server 3 I cannot access port 993 via the public IP. I can however access port 22 from the public IP. I don't understand why is that the case. I have no other strange firewall rules that might be getting in the way and I don't see what makes server 3 special in this regard compared to servers 1, 2, 4 and 5. Any help would be much appreciated.

Thank you!



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  • There is the auto-generated rule from creating the DNAT via the assistant. Notice that SSH for example works fine. I don't see any other rules that might be getting in the way. Also notice that other internal hosts can get to IMAPS via the public IP and I don't see anything special about this host.

  • Still not sure what is going on, there is a loopback rule for this that should take care of it. It is the same for all the other services and internal hosts, from IP 192.168.10.10 I can telnet the public IP at 993 and it will work fine but it won't work for IP 192.168.10.11. However from 192.168.10.11 I can telnet 22 or 80 the public IP and the port forwarding to the internal server will work just fine! Is port 993 special?