When I'm ssh'ed into one of our office servers (which run Fedora 10) from home, my session times out after a fairly short period of activity (5 minutes or so). I've tried using TcpKeepAlive on the client side, to no effect.
The thing I don't understand is that if I'm in the office on the company LAN, I can leave a session inactive all day without it timing out, so the behaviour seems to be dependent on my location.
Any ideas why this is happening and how to prevent timeouts when I'm not on the LAN ? I'm using the Terminal client on Mac OSX if that helps.
UPDATE – Dave Drager's suggestion of using the ServerAliveInterval set to non-zero with TcpKeepAlive=no worked for me. Regarding some of the other answers, the ClientAlive… settings aren't accepted by the Mac OSX SSH client.
Best Answer
There is a good writeup on this problem here.
They recommend:
or:
However, I do have an issue at my work site where I get disconnected from sessions, where at home they are fine. I believe my firewall (SonicWall) may be flucking with TCPKeepAlive, maybe because of NAT.
My SSH client, SecureCRT, fortunately has an option for a "NO-OP" protocol, which I believe basically sends a command that doesn't do anything to the server. By manually enabling this I am able to remain connected. Not sure what the MacOSX terminal client has that is similar to that. There is a writeup on how to implement "NO-OP" on command line.
Finally, you may wish to use Wireshark or other sniffer to watch your actual TCP connection to find out what is going on with it. That would be the final way to see why it is still disconnecting occasionally.