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 http://www.snailbook.com/faq/mtu-mismatch.auto.html and
try setting the MTU of the problem machine to 576 to see if the problem
goes away.

--
Darren Tucker (dtucker at zip.com.au)
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.



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