>I am not sure what the flag for ip_forwarding quite means. I know
>the concept and the echo "1" >/proc....
>I don't remember quite where it echoes to, but that's Debians job,
The exactly echo is (I am checking in 2.2.12) echo "1"> /proc/sys/net/ipv4/ip_forward.
>Does ip_forward=yes simply set this echo "1" >/proc... to be
The kernel option ip_forward enables the kernel to resend packets
received with a destination address accesible but not local (that is,
enables your host to do routing work). The 'echo "1">...' is the way
to say to the kernel that you really want it to do this. Unless you
put 'echo "1"...' somewhere, the kernel will not start to
resend/forward ip packets although it has the necessary code built
in. They are both necessary but not the same.
You can thing of ip_forward=yes as a "kernel-compile-level" enable and
of 'echo "1" ...' as a "network-configuration-level" enable.
So, if you are setting up a router or something like that, you should
select ip_forwarding before compiling the kernel, and then put
the "echo ..." somewhere or let debian conf to do so.
It is described somewhere in the kernel menuconfig/xconfig documentation.