Howto get Apple Remote Desktop to work behind a router
From How2s
If you are running Apple Remote Desktop (http://www.apple.com/remotedesktop/) behind a router, firewall, or NAT, you will find out that it is not accessible from the outside internet. However, if you want to be able to access your machine from the internet, you will have to set your router up for port forwarding. This basically means that you are accessing the router and it is passing all the traffic on the respective ports to your machine on your LAN (Local Area Network). Therefore, you need to know the IP address of your computer on the LAN. Depending on your situation, it might be best to make it static in the settings by changing from "DHCP" to "Manual".
I also recommend using Dyndns (http://www.dyndns.org). Most routers support dyndns nowadays. You need to open an account at dyndns.org (http://www.dyndns.org) (e.g., yourname.dyndns.org), and then enter your domain name, username, and password into your router. This allows you to access your router without knowing the IP address (which can change any time anyway).
Apple Remote Desktop uses the following TCP and UDP ports for the functions indicated. These ports need to be forwarded to your local machine in your router configuration.
| Port | Protocol | Function |
| 5900 | TCP | Observe and Control |
| 5900 | UDP | Send screen, share screen |
| 3283 | TCP | Reporting |
| 3283 | UDP | Everything else |
| 22 | TCP | Encrypted file transfer, observe, and control (via SSH tunnel) |
Remember: Your IP address on the LAN must start with 10, 192, or 172 (e.g., 10.1.1.14, 192.168.1.34, or 172.16.15.83)
More information about how to set up port forwarding on your router. (http://www.portforward.com/routers.htm)
