Troubleshooting NAT Port Forwards

If problems are encountered while attempting a port forward using pfSense® software, try the following.

  1. If the Port Forwards guide was not followed exactly, delete anything that has been tried and start from scratch with those instructions.

  2. Port forwards do not work internally unless NAT reflection has been enabled. Always test port forwards from outside the network, such as from a system in another location, or from a 3G/4G device.

  3. Edit the firewall rule that passes traffic for the NAT entry and enable logging. Save and Apply Changes. Then try to access it again from the outside. Check the firewall logs (Status > System Logs, Firewall tab) to see if the traffic shows as being permitted or denied.

  4. Check the states table under Diagnostics > States, filter on the source, destination, or port number to see if any entries are present. If entries are present that appear to match the NAT performed by the port forward, then the firewall is accepting and translating the traffic properly, so look at internal issues (e.g. client firewalls, etc, see below.)

  5. Use a Packet Capture or tcpdump to see what is happening on the wire. This is the best means of finding the problem, but requires the most networking expertise. Navigate to Diagnostics > Packet Capture to capture traffic, or use tcpdump from the shell. Start with the WAN interface, and use a filter for the appropriate protocol and port. Attempt to access from outside the network and see if it shows up. If not, the ISP may be blocking the traffic, or if Virtual IPs are involved they may have an incorrect configuration. If the traffic is seen on the WAN interface, switch to the inside interface and perform a similar capture. If the traffic is not leaving the inside interface, there is a NAT or firewall rule configuration problem. If it is leaving the interface, and no traffic is coming back from the destination machine, the target system’s default gateway may be missing or incorrect, it may not be listening on that port, or it may have a local firewall (Windows Firewall, iptables) blocking the traffic. For certain types of traffic return traffic may be seen indicating the host is not listening on that port. For TCP, this would be a TCP RST. For UDP, it may be an ICMP Unreachable message.

Common Problems

  1. NAT and firewall rules not correctly added (see Port Forwards)


    Do NOT set a source port

  2. Firewall enabled on client machine

  3. Client machine is not using pfSense as its default gateway

  4. Client machine not actually listening on the port being forwarded

  5. ISP or something upstream of pfSense is blocking the port being forwarded

  6. Trying to test from inside the local network, need to test from an outside machine

  7. Incorrect or missing Virtual IP configuration for additional public IP addresses

  8. The pfSense router is not the border router. If there is something else between pfSense and the ISP, the port forwards and associated rules must be replicated there.

  9. Forwarding ports to a server behind a Captive Portal. An IP bypass must be added both to and from the server’s IP in order for a port forward to work behind a Captive Portal.

  10. If this is on a WAN that is not the default gateway, make sure there is a gateway chosen on this WAN interface, or the firewall rules for the port forward would not reply back via the correct gateway.

  11. If this is on a WAN that is not the default gateway, ensure the traffic for the port forward is NOT passed in via Floating Rules or an Interface Group. Only rules present on the WAN’s interface tab under Firewall Rules will have the reply-to keyword to ensure the traffic responds properly via the expected gateway.

  12. If this is on a WAN that is not the default gateway, make sure the firewall rule(s) allowing the traffic in do not have the box checked to disable reply-to.

  13. If this is on a WAN that is not the default gateway, make sure the master reply-to disable switch is not checked under System > Advanced, on the Firewall/NAT tab.

  14. WAN rules should NOT have a gateway set, so make sure that the rules for the port forward do NOT have a gateway configured on the actual rule.

  15. If the traffic appears to be forwarding in to an unexpected device, it may be happening due to UPnP. Check Status > UPnP to see if an internal service has configured a port forward unexpectedly. If so, disable UPnP on either that device or on the firewall.