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Carlos1010

What is port-forwarding?

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Posted · Original PosterOP

Hi all,

When I was looking at VPN's, I saw that there was an option with port-forwarding when buying it. Then I thought, what is port forwarding? Searching this term on google just gives really short explanations that I don't really understand. Can someone give me an example where you would have to use port forwarding as an option when doing something? I am very confused about this topic.

Thank you so much (In advanced)

 


I'm part of the "Help a noob foundation" 

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In computer networks, port numbers are used to talk to a specific service that may be running on a computer. For example, 80 is a common port for computers to talk in HTTP which delivers web pages. 22 is a common port for remote shell logins.

 

In a LAN, despite every computer having a different IP address, they all share the same external IP address. So if your external IP is 123.123.123.123, every computer in your LAN will be seen as the rest of the world as 123.123.123.123, even if one computer in the LAN claims it's 192.168.1.3 and another 192.168.1.42.

 

The problem is when the internet wants to initiate communication to one of your computers in the LAN. Since every computer in the LAN is seen to the rest of the world as 123.123.123.123, your router doesn't know who to forward the data to. However, since the other computer is usually trying a specific service, it will use a port. So if you have a web server set up, it'll listen for communication requests on port 80. The other computer will connect to 123.123.123.123 port 80. The router is then set up so that any requests on port 80 will forward traffic to the web server you set up. Let's say the web server on the LAN is 192.168.1.42. So all traffic from the internet to 123.123.123.123 port 80 will be forwarded to 192.168.1.42.

 

I suppose a real world quasi analogy is think of your LAN as an apartment building. Every apartment in it though shares the same street address. So in order for mail addressed to you to get to you, you have to tell the postal service which apartment number you're in so that all mail coming in to that street address and apartment number goes to your mailbox.

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2 minutes ago, M.Yurizaki said:

I suppose a real world quasi analogy is think of your LAN as an apartment building. Every apartment in it though shares the same street address. So in order for mail addressed to you to get to you, you have to tell the postal service which apartment number you're in so that all mail coming in to that street address and apartment number goes to your mailbox.

I have been trying to come up with something like this for years now, to dumb it down as far as possible for not-so-techy-people to understand. Thanks a lot!!!!

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port forwarding is basicly when you open up a port on your firewall to let traffic in and out 

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