Let me explain you my understanding here,
IP addres
there are two types of IP address
1. Static IP – permanent IP address (usually you have to pay for the provider)
2. Dynamic IP – IP changes every time you restart router (most usual one)
In general, every computer has two IP address, one is internal (private) another is external (public). Only your router knows your internal IP address and the computers that are connected to your router can communicate with your computer. In case any computer out side of your router wants to communicate your computer then it can approach you only via external IP address. For instance if you type ‘http://www.whatsmyip.org’ in your web browser then it will reveal your external ip.
So whom ever has Dynamic IP address, they must have different internal (ex: 192.168.1.23) and external IP (ex: 35.129.112.111) address. However if you have a static IP address then both of them are same.
What’s the problem now? Most of the routers usually does not allow the external request to communicate the local computer via port number 22 (default ssh port) and also few other ports like 548 (afp). If you want to ssh your computer from outside then it is a problem.
Here comes port forwarding to solve this problem above. It is nothing but you will say to your router “hey forward the external port 22 request to my computer”. Now the internal IP address plays the important role. If your router connected to many computers then make sure that every computers has their unique internal IP address, if not then just change it to any.
1. Open your router configuration page in a web browser by entering http://192.168.1.1, upon requesting user name and pass, file with admin and admin. I hope most of the router has the same user name and pass, if you can’t login successfully then you must contact the manufacture.
2. Depends on router you can easily find the port forwarding page, more interestingly there’s an website which explains the port forwarding for several routers. If you are lucky then you can find your router configuration in their webiste; http://portforward.com/.
3. Here I’ll explain you the port forward configuration for SIEMENS SL2-141-I ADSL WLAN Router.
4. Open web browser, type in http://192.168.1.1 and hit enter.
5. Now the browser should ask you the user name and password. Don’t copy and paste the following username and password, it doesn’t work
username : alice@13184
passwort : hnto$mgmt@lice
3. Click on Advanced on the top of the page followed by Virtual server on the left side of the page.
4. Click on Add, choose User defined. Enter the name of the program into the User defined box. It doesn’t really matter what you put into this box, but something that will remind you why these ports are being forwarded would be a good idea. Select ALL from the From Internet Host IP Address drop down box. Enter the ip address to forward these ports to into the Forward to Internal Host IP Address box. If you are forwarding ports so you can run a program on your computer, you should enter your computer’s ip address into that box. Use the Protocol drop down box to select the protocol type of the ports you are forwarding. If you are forwarding a single port, enter that port number into the External Port Start, External Port End, Internal Port Start and Internal Port End boxes. If you are forwarding a range of ports, enter the lowest number of the range into the External Port Start and Internal Port Start boxes. Then enter the highest number of the range into the External Port End and Internal Port End boxes. When you are finished, click the Apply button.
Here’s the screen shot of my settings.
that’s all, hope it is your for you.
Useful links
http://portforward.com/
“Well known” TCP and UDP ports used by Apple software products
Other useful ARD links
“How to” access Macbook by ARD via Internet
Is there a simple/cheap way to connect to another Mac?
How to securely control another Mac over the internet Internet
Make remote tech support as simple as possible
வழிப்போக்கன்-Mac OSX 