Re: NAT & FORWARDING

[Srinivasa Hebbar <sshebbar@yahoo.com>]

Dear John,

Your solution works fine for me.
Actually, I want to know how I can build a NAT rule 
which will have "and" condition.

My box has atleast 50 interfaces and I want to do NAT on
all interfaces except "eth0" and "xpeth0"

So I want some thing like, 

iptables -t nat -A PREROUTING  -i ! (eth0 && xpeth0)  -p tcp --dport 3021 -j 
ACCEPT

But, the iptables doesn't take the above syntax.

Could you give me some hint how to solve the above probelm.
One solution is to add the rule for all other 48 interfaces
to accept the connection on port 3021. I can't use wildcards because each 
interface name is different.

Regards,
S. Hebbar.


> On Thu, 2004-01-29 at 09:23, Srinivasa Hebbar wrote:
> > Hello,
> >
> > I believe that the NAT PREROUTING and POSTROUTING will
> > always takes place for all the incoming/outgoing packets
> > irrespective of whether the packet is destined to the node or not.
> >
> > I have a situation that if the dest. IP address of the packet is
> > for the local node, then apply NAT rule, otherwise it should simply
> > forward the packet according to the routing table.
> >
> > How can I achieve the above?
> >
> > Any help is very much appreciated.
> >
> > Regards,
> > S. Hebbar.
>
> Could you give a little more information, please.  That would help us
> understand why you would want to NAT a packet destined for the local
> node itself and why one would not simply NAT only if the destination
> address matched the local node.  Thanks - John