Re: simple ip_forward didn't work

[Nathan Barham <nathan@sleepygeek.com>]

Guenter.Sprakties@team4.de wrote:

> The tests were made by one windows machine per internal subnet. Ifconfig 
> shows that all was up and running with the right value, route looks good 
> also. We could ping our test machines in both subnets as well as they 
> could ping  the server. After this we tried ip_forward by echo 1 > 
> /proc/sys/net/ipv4/ip_forward and tried to ping one windows machine from 
> each other. Didn't work. After testing we achieve the following picture:
>
> - Win client1 (172 subnet) could ping the server on the server's 172 
> subnet address
> - Win client2 (192 subnet) could ping the server on it's 172 and its 192 
> subnet address
> - no client could ping the 212 address
> - setting of ip_forward to 0 or 1 had no influence to our results

So basically you turned forwarding on and it doesn't work.  You probably 
thought of these already but it's all I can think of ATM...

Did you set your FORWARD chain policy to DROP and forget to allow the 
traffic to/from your subnets?  Do you have a logging rule in place for 
packets dropped in the FORWARD chain, and if so is it logging anything?

Also note that in Debian echo "1" > /proc/sys/net/ipv4/ip_forward can 
also be achieved by setting ip_forward=yes in /etc/network/options.

-Nathan