Accessing local FTP server through external IP bandwidth usage

[Ambicky Burger]

Hi all,

 

I currently have a raspberry pi hooked up to my external drive which holds all of my media. I set up an ftp server and forwarded the correct port in my router.

All is well and I can perfectly access my external drive from anywhere in the world using my external ip adress. Here comes the question:

 

If I am connected to the local network in which the FTP server is located, but I access it through the external IP (instead of the local ip address), will it use up any of my limited monthly internet bandwidth (100 GB)?

Or should the router be smart enough to route all traffic locally, not affecting my monthly bandwidth?

 

Very curious for the answer!

[manikyath]

it depends on what your router does exactly, and where the bandwidth is counted.

[jj9987]

If you are in the same network, you do not need to use the external IP and it wouldn't use the bandwidth if you used the local address.

[GodSpoon]

It "should" do it locally, but it depends on how the router handles that traffic, if it has dd-wrt or similar firmware you can check that bandwidth allocation

[sushisharkjl]

Your Pi has a local IP, if you access it through the local IP you will not use your bandwidth cap.

 

If you port forward it and access it through your public IP then yes, you will use your bandwidth.

[brwainer]

Accessing a local server from a local client via the external IP is called "Hairpin NAT". The router should handle it locally, I can't really see any setup where it would send out to the default gateway then come back. Actually if it made it to the ISP, the packet would probably just be dropped since the source IP would be a private IP address which is non-routable on the internet.

[Tosa]

Given the nature of networking, I believe the router will see that the packets destination is to itself, and will thus deliver them directly to itself, and then forward it to the raspberry pi. The ISP will see none of it.

 

I've noticed that when I do this with my router (Asus RT-N66U), it's NATing it with it's own internal IP.

[Ambicky Burger]

On 2/29/2016 at 9:58 PM, brwainer said:

Accessing a local server from a local client via the external IP is called "Hairpin NAT". The router should handle it locally, I can't really see any setup where it would send out to the default gateway then come back. Actually if it made it to the ISP, the packet would probably just be dropped since the source IP would be a private IP address which is non-routable on the internet.

Thanks, that's what I was guessing but I wasn't sure. Never heard of Hairpin NAT before.