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Nmap shows that some ports are open, but when I test if the ports are open from the internet (using certain tools) it says that the ports are closed. Struggling quite a bit, can anyone explain why this would be the case?

this is a screenshot of nmap

  • What tools are you using to check the ports that nmap reports to be open? – TheJulyPlot Feb 14 '17 at 14:39
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    You're testing from within your network using nmap, and from outside your network using an online tool. The online tool can usually only see your router. – Matthew Feb 14 '17 at 14:40
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    Your hostname latinababa.ddns.net resolves to the private IP address 192.168.1.17 which you cannot reach from outside your local network. Thus the tools cannot get there from the Internet. – Hacktiker Feb 14 '17 at 15:37
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The main function of routers is to connect two networks. Usually, there's the Internet side and the LAN side. And usually each side has its own physical interface and always its own IP address space.

Assuming you have a typical network configuration, in your example:

  • The LAN address is 192.168.1.17, so the network is probably 192.168.1.0/24. This address range corresponds to the Wi-Fi interface and the cable slots, to which you can connect a laptop using an Ethernet cable.

  • The Internet side is represented by a public IP, by which your machine is addressed by your ISP. And the Internet cable has its own socket, into which you need to plug it.

These two networks have separate configurations on the router, which don't have to be symmetrical. Services on the machines in these two networks can be visible to the machines on the other side, but only if the router makes them visible.

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You must have a DNS entry for latinababa.ddns.net on your local network resolving to your LAN IP 192.168.1.17 while on the internet it resolves to your public IP. Ports can be open on your LAN that aren't open past your router. Opening these ports is called "port forwarding".

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