telnet/ssh disconnects... Possible NAT teardown?

Mike Klinke lsomike at futzin.com
Thu Feb 5 23:20:05 UTC 2004


On Thursday 05 February 2004 16:49, Jeremy wrote:
> Alright, I'm using Fedora Core 1.  My box is setup as a router for
> the rest of my network.  It has two network cards, one 10 base card
> connected to a cable modem, and another 10/100 connected to my
> network switch.  I have iptables setup to do masquerading.
>
> The problem...
>
> Telnet/SSH connections to the machine, from the outside world,
> disconnect after 5-10 minutes of inactivity.  For example, I can
> have 3 SSH connections to my box, neglect one window for a few
> minutes, and when I go to that window and start typing, I get a
> message from PuTTY saying I got disconnected.
>
> I've looked extensivly on the net trying to figure out what's wrong
> and how to fix it.  I've come across a couple sites saying that
> this could possibly be caused by a 'NAT teardown'.  I'm new to
> iptables and NAT, so i'm not exactly sure what this means.  I was
> under the impression that NAT timeouts on CONNECTED connections was
> like 5 days of inactivity before it would drop.  When I cat
> /proc/net/ip_conntrack, i see my connections, and I see they have
> very high timeouts.
>
> I've looked through the iptables man page, as well as the
> iptables/netfilter website, and i can't find anything relevent to
> this.  Does anyone know how I might fix this?
>
> -Jeremy
> 


Have you tried:

using an application other than Putty? 
from another machine? 
connecting in the opposite direction?
watching the connection via tcpdump?

These may help to see what's going on.

Regards, Mike Klinke





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