ip forwarding and iptables

I have 2 PCs: one configured as gateway (PC1) and the other one (PC2) configured to use PC1 as gateway. PC1 runs a custom linux
distribution. It has ip forwarding enabled (e.g. by echo 'net.ipv4.ip_forward = 1' >> /etc/sysctl.conf).
As far as I understand, I do not need to do anything else to make the kernel route traffic to and from PC2, right?
However, if I have one PC more - PC3, and I do not wnat to route traffic to and from it I need to configure the kernel, e.g. with
the help of iptables. Now if I do so, i.e. use iptables to configure the kernel, save the iptables configuration, setup the system
to reload it at startup (using the init.d scripts), is there any moment (during system startup) when ip forwarding has been enabled
but the iptables configuration has not yet been loaded and traffic could be routed to and from PC3?

On Mon, 15 May 2006 22:16:56 +0300, Angel Tsankov wrote:

> I have 2 PCs: one configured as gateway (PC1) and the other one (PC2) configured to use PC1 as gateway. PC1 runs a custom linux
> distribution. It has ip forwarding enabled (e.g. by echo 'net.ipv4.ip_forward = 1' >> /etc/sysctl.conf).
> As far as I understand, I do not need to do anything else to make the kernel route traffic to and from PC2, right?
> However, if I have one PC more - PC3, and I do not wnat to route traffic to and from it I need to configure the kernel, e.g. with
> the help of iptables. Now if I do so, i.e. use iptables to configure the kernel, save the iptables configuration, setup the system
> to reload it at startup (using the init.d scripts), is there any moment (during system startup) when ip forwarding has been enabled
> but the iptables configuration has not yet been loaded and traffic could be routed to and from PC3?

Check your rc#.d dir for the order that things are started. normally
iptables is started before the network interfaces are.


--

Regards
Robert

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