Comments on: Keeping Your SSH Connection Alive

By: How-To: Share remote *nix files with local Windows Users | Heart of the Mix

How-To: Share remote *nix files with local Windows Users | Heart of the Mix — Thu, 17 Nov 2011 23:24:13 +0000

[...] the TCP Keep Alive method, or the ServerAliveInterval method. Both of which are outlined briefly here. I prefer ServerAliveInterval as it’s easier for me to remember. Add the following two [...]

By: Jordan

Jordan — Tue, 26 Jul 2011 23:32:06 +0000

Thank you!! =) I’ve been using ssh for years, but have recently started delving into its less common features. This is a gem… =)

By: The GuiGui's show » SSH : du port forwarding au VPN bon marché

The GuiGui's show » SSH : du port forwarding au VPN bon marché — Thu, 24 Feb 2011 20:34:38 +0000

[...] Encore une fois, je ne réinventerai pas la roue puisqu’une recherche sur Google vous conduira sur ce blog : Aaron Toponce : Keeping Your SSH Connection Alive. [...]

By: Tim Smith

Tim Smith — Mon, 07 Feb 2011 10:25:39 +0000

Dr X,

The point of this work around is to get around firewalls detecting the SSH sessions as idle, and dropping them out of their state tables. Then when the client tries to send it’s next packet, the firewall will drop it, as it will see it out of state.

You can disable this behaviour on firewalls, but that is there job So better off to adjust on the clients / applications

Cheers,

Tim.

By: dr. x

dr. x — Sat, 18 Jul 2009 03:12:14 +0000

hmmm… i *think* (am no expert) you really would want to turn OFF TcpKeepAlive, not turn it on.

If you have it ON the client/server will notice when the connection is unresponsive and… as seems to be implied by the man page, close the socket. Which is what some people find annoying… as expressed in the man page entry below.

from the man page for ssh_config:

TCPKeepAlive
Specifies whether the system should send TCP keepalive messages
to the other side. If they are sent, death of the connection or
crash of one of the machines will be properly noticed. This
option only uses TCP keepalives (as opposed to using ssh level
keepalives), so takes a long time to notice when the connection
dies. As such, you probably want the ServerAliveInterval option
as well. However, this means that connections will die if the
route is down temporarily, and some people find it annoying.

The default is “yes” (to send TCP keepalive messages), and the
client will notice if the network goes down or the remote host
dies. This is important in scripts, and many users want it too.

To disable TCP keepalive messages, the value should be set to
“no”.

By: GNUWIX

GNUWIX — Tue, 24 Mar 2009 06:19:51 +0000

So, with the TCPKeepAlive option passed to SSH, the SSH client will send an encrypted packet to the SSH server, keeping your TCP connection up and running.

This is inaccurate.. This is a TCP option and will not send “an encrypted packet”

Otherwise pretty good post thank you

By: Hans

Hans — Thu, 17 Apr 2008 16:41:20 +0000

autossh has its place, but its job is to automate reconnecting in the event of a disconnect, not keeping a connection alive.

By: Kurt

Kurt — Thu, 17 Apr 2008 12:16:56 +0000

What about using autossh?

By: Aaron

Aaron — Wed, 16 Apr 2008 21:45:59 +0000

@Bjørn Grønbæk- It does. Add either of those options to your ~/.ssh/config file. The sshfs utility reads that file, and adds the options to the connection, as sshfs just just an ssh directory mounted to a local dir on your filesystem.

By: Steve

Steve — Wed, 16 Apr 2008 20:37:43 +0000

excellent!

By: Bjørn Grønbæk

Bjørn Grønbæk — Wed, 16 Apr 2008 18:45:24 +0000

Thanks man. I’m having the exact same problem here at University of Southern Denmark. Stupid network…

It really screws up your system if you mount a remote folder with sshfs, and the connection is terminated by inactivity. It would be nice if sshfs had some option just like those above. But your advice is a great help anyway.