we are using iptables, but as far as I know there is no timeout set on our iptables.

this is happening sporadically.

I thought that if it is related to network we will receive some kind of connection error and not freezing screen.

Thanks for help

Simon Jolle wrote: 
2007/12/12, Centos <centos@unixplanet.biz>:
  
My ssh terminal froze some times, and I was thinking it might be related
to centos ,
but now I found that even ubuntu users experiencing the same problem.
    

Is there a firewall between your client and the server (that kills the
session after inactivity)? Try the keep alive option.

cheers
Simon