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So I'm trying to set up SSH access to a friend's server, and we've learned from his ISP (SureWest) that their modem is bridged. Next, the router (Linksys E2000) was set up for port forwarding.

No outside access. We then tried DMZ to the server's IP. No go.

Then, we flashed the router with DD-WRT, still convinced it was a router issue. Port forwarding didn't work, and neither did DMZ.

At every step, we've had LAN and loopback access (via WAN IP). What else could be the issue?

Thanks in advance :)

Extra info: Ubuntu Server, Comtrend NexusLink 5631 modem

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Try step by step to debug the problem. I would first start the ssh service on the dd-wrt modem and find out if I can connect on it. If you can't that means the ISP is blocking the 22 tcp port. To confirm that try to run the service on a different port. Then if even that doesn't work call the ISP to unblock the port. If the connection works then check if the port forwarding works fine or/and check the setting on the server side. – golja Jul 27 '12 at 2:11

Use tcptraceroute to find out where the packets are filtered:

Run from outside network:

tcptraceroute friendIP 22
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