Why doesn't my port forwarding rule work even though I set it up correctly?

The two most common causes are a device IP that changed after a router reboot (fix with a DHCP reservation) and double NAT, where your router sits behind another router or ISP modem that also needs a matching rule, or needs to be switched to bridge mode.

Should I forward TCP, UDP, or both?

Match the protocol the service actually uses. Web servers and RDP use TCP, most game and camera streaming protocols use UDP or both. Forwarding both when only one is needed is not harmful, it just opens a slightly wider path than necessary.

Is it safe to forward a port to a device on my network?

Only forward ports for services you intend to expose, keep the device's software updated, and avoid forwarding to devices with default or weak passwords. Forwarding a port makes that specific service reachable from the internet, so only open what you actually need.

Port Forwarding Generator – Build a NAT Rule Free

Port Forwarding & NAT Rule Generator

Fill in your device and port details to get the exact rule to enter in your router, plus a checklist of the mistakes that usually break it.

Common service (optional)

Device LAN IP address

Internal port

External port

Protocol

My router connects to another router, gateway, or ISP modem before reaching the internet (double NAT)

Port Forwarding & NAT Rule Generator

What This Tool Does

Port forwarding rules all follow the same shape: an external port on your router’s public IP gets mapped to an internal IP address and port on your local network. This tool takes the device and ports you want to expose and produces the exact values to type into your router’s admin panel, along with a checklist built from the specific mistakes that most commonly break a forward: missing DHCP reservations, protocol mismatches, and double NAT.

Reading the Result

The three-box flow shows the translation in plain terms: a request arrives at your router’s public IP on the external port, the NAT rule rewrites it to your device’s private IP and internal port, and the device answers as if the request came from your local network. The config table below it lists the field values in the order most router admin panels ask for them, so you can copy them in directly.

Why Port Forwarding Breaks

The device’s IP address changed. Most routers assign LAN addresses dynamically through DHCP. Unless you set a DHCP reservation (sometimes called a static lease) for that device, it can get a new IP after a reboot, and the forwarding rule keeps pointing at the old one.
Wrong protocol. A rule forwarding TCP does nothing for a UDP-only service, and vice versa. When you are not sure, forwarding both is safe, just wider than strictly necessary.
Double NAT. If your router itself gets its internet connection from another router, mesh gateway, or an ISP-supplied modem/router combo, a single forwarding rule usually is not enough. The upstream device also needs a matching rule, or needs to be switched into bridge or pass-through mode so it stops performing its own NAT.

Related Tools & Guides

New to NAT and port forwarding? Start with What Is NAT? and Port Forwarding Explained for the concepts behind this tool. Check whether a port you forwarded is actually reachable with an external port checking tool, look up what a specific port number is normally used for in the Port Number Reference, or read the deeper walkthrough of firewall and traffic-filtering concepts in What Is a Firewall?. If devices keep dropping off your network after setting up port forwarding, our network troubleshooting guide covers the next steps.