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I'm trying to run an sshd behind a home router (a D-Link DIR-655). Whenever I use the router's configuration program to forward port 22 to the box running sshd, the web becomes inaccessible from all computers behind the router. What might cause this problem? (I'm a beginner when it comes to home networking and server setup.)

Also I couldn't determine whether this belonged on SuperUser or ServerFault; I went with SuperUser since it's a home problem. Sorry if that was incorrect!

Steps I took:

After logging into the router, I went to the "Advanced" tab and then to the "Virtual Server" screen. I filled Public and Private port settings with the number 22, set Protocol to both, set the IP Address to the server box's LAN IP (, checked the enable box, and left all other settings as-is.

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This is definitely a SU type question, you're in the right place. Can you give us a walkthrough of what steps you took to forward the port? We can follow along using the emulator here: <>; – K.A Jan 13 '13 at 18:45
@K.A I've updated the answer to describe what I did, and thanks for taking the time to try and help – leo-the-manic Jan 13 '13 at 19:01
Can you provide us with more information on how the web becomes inaccessible? Do you get an error message from your web browser? Is it only websites (HTTP/S) that are inaccessible, or do things like FTP also go down? Any details on this will help us. – K.A Jan 13 '13 at 19:07
Probably not the problem, but you only need TCP for ssh to work. – BubuIIC Jan 13 '13 at 19:10
ping gives the error "Could not find host," and Firefox says "Server not found." – leo-the-manic Jan 13 '13 at 19:14

I suspect the loss of connectivity was because your router was restarting after applying the changes. Try making some other change (Forward, say, port 10000 to an IP that isn't assigned) and applying the change. See if the connections are all lost. If so, wait a little while and they should return after the router finishes restarting. Unfortunately there is no prefect solution to this, just to make sure there are no critical connections (large file transfers, VoIP calls, etc.) going on when making changes to your router's configuration.

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