Re: ssh communication issue

On Fri, Jan 06, 2006 at 05:05:29PM -0500, Larry Irwin wrote:
> -Hopefully this is the right list-
> Our ssh connections work fine on all our servers when we connect via
> the -local- network.
> But, when we ssh from the -internet-, there are long pauses where i/o is
> not displayed/echoed to the screen on our Debian servers.
> We experience 10 to 30 second pauses after a screen or 2 of display on
> Debian Etch kernel 2.6.12, SSH-2.0-OpenSSH_4.2p1 Debian-5.
> We have same issue, with slightly shorter pauses, on a Debian Sarge kernel
> 2.4.18, OpenSSH_3.4p1 Debian 1:3.4p1-1.woody.3.
> We do not experience the problem on a SCO OS5 3.2v5.0.5 kernel,
> OpenSSH_2.2.0p1
> Also, if we ssh to SCO first, then locally ssh to Debian, the pauses do not
> occur...
> So it definitely has nothing to do with the network or infrastructure or
> the load on any server, etc.
> It is something to do with either Debian or OpenSSH and only is triggered
> when the IP source IP is outside the LAN.
> Does anyone know what might me contributing to the screen IO issue?

It's possibly an MTU issue which comes good when Path MTU Discovery
kicks in. Read and
try setting the MTU of the problem machine to 576 to see if the problem
goes away.

Darren Tucker (dtucker at
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4 37C9 C982 80C7 8FF4 FA69
Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.