[lug] Weird Masquerading Problem

[D. Stimits]

George Sexton wrote:
> 
> I have this weird problem on a machine that I can't figure out.
> 
> For some reason, masquerading just stopped working. It was working fine,
> then one day there was a crash, and then it didn't work any more.
> 
> I have done a pretty thorough security check so I am fairly confident the
> box has not been hacked. I have checked current rules using IPCHAINS and
> everything looks good. I also tried replacing the NIC on the theory that
> maybe there was something strange in the NIC driver (EEPro100 which has been
> notoriously bad lately).
> 
> The only thing I can think is that there is another box with the same IP. I
> shut down the Linux box, and waited for a while, and didn't see anything
> that looked like another box on the same IP address.  This one has me really
> stumped. I would appreciate any ideas.
> 
> George Sexton
> MH Software, Inc.
> Voice: 303 438 9585
> http://www.mhsoftware.com
> 
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You might want to see if it is enabled still:
cat /proc/sys/net/ipv4/ip_forward

"1" is on, "0" is off.

If it isn't on, the "on" file is in different spots for different dists,
which you didn't mention the flavor.