Fedora templates have a weird issue where the packet counter on the sys-net nat FORWARD chain does not increment. The PREROUTING chain does increment.
The commands work, my configuration is correct, as it was working on R3.2 and does work on R4.0 if using an older debian-8 template for sys-net and sys-firewall. Using Debian-8 template that came with Qubes 4.0 RC2 or earlier.... does work as expected. It has iptables 1.4, while fedora has iptables 1.6. I can go back and forth between fedora-25/26 and debian-8, and it will work when on debian. Debian-9 has a weird issue where the counter on the sys-net FORWARD chain does get incremented, but nothing is sent to sys-firewall. Verified with tcpdump. Sys-Net: iptables -t nat -A PREROUTING -i ens5 -p tcp -d <outside_ip_of_sys-net> --dport 2200 -j DNAT --to-destination <ip_of_sys-firewall> -m comment --comment 'PortFwd' iptables -I FORWARD 2 -i ens5 -p tcp <ip_of_sys-firewall> --dport 2200 -m conntrack --ctstate NEW -j ACCEPT -m comment --comment 'PortFwd' Sys-Firewall: iptables -t nat -A PREROUTING -i eth0 -p tcp -d <ip_of_sys-firewall> --dport 2200 -j DNAT --to-destination <ip_of_AppVM> -m comment --comment 'PortFwd' iptables -I FORWARD 2 -i ens5 -p tcp <ip_of_AppVM> --dport 2200 -m conntrack --ctstate NEW -j ACCEPT -m comment --comment 'PortFwd' Target AppVM: iptables -I INPUT 5 -p tcp --dport 2200 -m conntrack --ctstate NEW -j ACCEPT -m comment --comment 'PortFwd' SYS-NET sudo iptables -vnL -t nat | grep 2200 ; sudo iptables -vnL FORWARD | grep 2200 3 180 DNAT tcp -- eth0 * 0.0.0.0/0 10.0.1.53 tcp dpt:2200 /* PortFwd */ to:10.137.0.6 0 0 ACCEPT tcp -- eth0 * 0.0.0.0/0 10.137.0.6 tcp dpt:2200 ctstate NEW /* PortFwd */ My configuration works flawlessly for many months on R3.2 and even works today when using debian-8 for my sys-net and sys-firewall. And yes, of course my net.ipv4.ip_forward is 1 -- You received this message because you are subscribed to the Google Groups "qubes-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to qubes-devel+unsubscr...@googlegroups.com. To post to this group, send email to qubes-devel@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/qubes-devel/609dfb2d-7d55-42c4-9641-206edf689d26%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.