IP forwarding drops out.

[hendrik@topoi.pooq.com]

I have my network front end running Debian sarge (yet, it's time to 
upgrade at lest to etch).  It's connected to the rest of the net by a 
DSL line.  I've set up port-forwarding to selected machines on my LAN 
for the convenience of certain games, and bittorrent, and I'd like to 
use it for some always-on applications.

But every now and then, once every week or two, the port-forwarding 
drops out, and I have to reestablish it by running the same script that 
gets run on startup.

Does anyone have any idea how to track down the problem?  I've looked at 
the system logs and not found anything suspicious.  But probably I don't 
know which logs to look in, or what to look for in them, and it would be 
as plain as day if I did.

If this is a known sarge problem, of course upgrading to etch would be 
the solution.

-- hendrik