[lug] dumb q....echo 1?

[hirsch at zapmedia.com]

j davis writes:
 > 
 > hi,
 > 
 > so im rebulding my firwall with the help of the best iptables how
 > to i have ever read 
 > http://www.boingworld.com/workshops/linux/iptables-tutorial (thats quite a 
 > few now). Anyway in a example script
 > this is used
 > 
 > echo "1" > /proc/sys/net/ipv4/ip_forward
 > 
 > so i think the text "ip_forward" is being written to /proc/sys/net/ipv4..
 > what is the "1" for? Also proc is the ram right? could some one explain
 > why i have to do this and what is really happening when i do this.

I think you have misunderstood that line. The command: echo "1"
will just print the numeral 1 on your terminal, so 
      echo "1" > /proc/sys/net/ipv4/ip_forward
will send the numeral to the file /proc/sys/net/ipv4/ip_forward.  

The /proc directory and its children are a direct line to the kernel,
and 1 is true.  So you are telling the kernel that it should activate
the ip_farward feature of it ipv4 (Internet Protocol 4, or the
standard internet netwroking stuff) part of the networking system.

In other words, "start doing IP forwarding".

Hope that clarifies it a bit,

--Michael