Problems with dynamic LAN IP addresses and external IP addresses

There is one minor problem with this setup. The Pi might get a new LAN IP address each time you restart it, making the Port Forwarding setting useless. To avoid this, most routers provide the Address Reservation setting. You can tell most routers that each time a device with a unique MAC address is connected, it should get the same IP address.

Another problem is that your Internet Service Provider (ISP) might assign new IP addresses to you each time you restart your router or for any other reason. You can use a dynamic DNS service, such as DynDNS, to avoid such problems. Most routers are capable of using dynamic DNS services. Alternatively, you can get a static IP address by contacting your ISP.