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I'm trying to ssh into my OS X laptop from my iPad using prompt. I have everything working when I'm on the same network, but when I try to access my computer from an outside network...everything fails.

I've followed various sets of instructions (such as those here How can I set my computer up for remote SSH access?). I have given my laptop a static IP starting with 10.x.x.x. I use an airport extreme and have port forwarded port 22. My airport shows an ip of 192.x.x.x. I've also set up no-ip. No-ip shows that I have an IP address like 67.x.x.x, while sites like https://www.whatismyip.com/ show an address of 173.x.x.x.

I've tried accessing the username.no-ip.com address. I've tried the 192 ip, the 67 ip, and the 173 ip. Nothing works.

Any thoughts?

Edit:

I set up the airport extreme with "Router Mode: DHCP and NAT". When I did that it assigned the DHCP range to 10.x and my laptop got an address in the 10.x range.

Port Forwarding: Both TCP and UDP 22 are forwarded.

I don't think that the airport extreme is the outermost device. I'm in an apartment building and have to connect my router to a port in the wall, so I assume that there's another router somewhere in the chain.

I can reach the internet from the Mac.

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Please specify in detail how you set up port forwarding. Is it TCP 22 to 10.x.x.x port 22? Is the AirPort base station the outermost networking device, or do you have e.g. your telecom's default router (without port forwarding) before it? Can you reach the internet from said Mac? Are you forwarding to the correct interface (i.e. Wi-Fi, ethernet)? –  Daniel Beck Aug 18 '12 at 17:44
    
@DanielBeck, I edited the question to reflect some new information. –  user1074057 Aug 18 '12 at 19:22
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1 Answer

up vote 1 down vote accepted

NAT allows to split one external IP into many local downstream IPs… The external world cannot directly start conversations with internal IPs Port forwarding allow certain protocols that reach the external IP to be forwarded to the internal IP that have connected the server able to handle them.

NAT can be cascaded then if you set port forwarding in your router but you have another NAT device upstream the exterior world will not ever reach your internal IP. In order to do that you have to set port forwarding on “both” NAT devices.

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So, if I'm understanding correctly, it will be impossible to do what I want to do since there is probably an upstream device that I don't have access to. –  user1074057 Aug 19 '12 at 17:07
    
if you in fact have an upstream NAT device and you do not have access to it then you won’t be able to make your stuff visible from Internet. Sorry. –  Pat Aug 21 '12 at 7:42
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