Port forwarding is a NAT rule that maps an external port on the router's public address to an internal IP address and port. Unsolicited inbound connections then reach a particular device, such as a game server or camera.
Why it matters
Behind NAT, outside hosts cannot start connections to your devices unless the router knows where to send them. Port forwarding provides that mapping. It also exposes the service to the Internet, so the target must be patched and protected. It fails if your ISP uses CGNAT or if the router has a double NAT.
Example
External 203.0.113.4:8443 -> Internal 192.168.1.30:443 (TCP)Visitors to https://203.0.113.4:8443 reach the NAS at 192.168.1.30. Use a port checker from outside your network to confirm the port is open.
Common mistakes
- Forwarding to a device whose local address changes. Reserve it in DHCP first.
- Exposing admin interfaces such as RDP or router panels directly.
- Testing from inside the LAN, which may not reflect external reachability.
Related
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