On a home private network, the router would have a private IP address something like this 192.168.0.1. On the home network there are 5 computers. Each has a local IP address 192.168.0.xx e.g. 192.168.0.2 – 192.168.0.6. But the computers themselves do not have a public IP, only the router does. So would it be possible for someone from an outside network to send a file to one specific computer in my home network? Like if they know the MAC address of the device.
And how is it that emails can reach e.g. outlook application installed on one computer with one IP address, but still be accessed from another computer with a completely different IP address.
In: 5
Also, something that hasn’t come up in the other answers but I think it’s worth mentioning is that all that stuff with the router having to track where answers go is not how the internet was designed to be used.
In theory, each device (computer, phone, router, servers, …) it’s supposed to have its own unique public IP. Unfortunately there’s only 4 billion IPv4 addresses available, and even though IPv4 is deprecated and should have long been replaced with IPv6 everywhere (which would have enough addresses for everyone), it’s still in use and these stupid workarounds and hacks are needed for IPv4 users.
With IPv6, assuming the firewall is configured correctly (of there is no firewall) you can absolutely directly connect to your computer from the internet.
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