ssh connections now freezing, if left idle for a few minutes

[Neal Becker]

M. Fioretti wrote:

> Greetings and... an admittedly very broad questions, maybe not
> even related to Fedora except for "what are the best tools on
> Fedora to diagnose this?"
> 
> I have this fedora desktop on which I usually keep open shells
> connected to several servers, via ssh (on different ports too).
> 
> Until 3/4 days ago, I could leave all of them "hanging" for
> DAYS, without typing anything at those prompts, and they'd
> remain alive and ready to accept commands. Now, all of them
> freeze if I leave them idle for more than a few minutes.
> Every other connection (email, web, etc...) has no problem.
> 
> I have also noticed that if I rsync via ssh several GBs of stuff in
> the same moments, from/to the same servers, with the same
> accounts, same ports... etc, THOSE operations work just fine,
> pretty quick too.
> 
> In other words, it's all and only the plain AND unattended
> ssh connections that systematically freeze.
> 
> I ran yum update, and that did not change anything. At this
> point, it is likely that either my ADSL provider and/or its
> modem are doing something funny, so the question is:
> 
> how could I discover what happened, and where?
> 
> Thanks,
> Marco

Possibly some intermediate middle-box (router) is set to timeout tcp 
connections?