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Re: Moving packets from one port to another



Hello James,

please excuse the incomplete mail. Ctrl+Return did not do what I
intended it to do. :\

James Allsopp <jamesaallsopp@googlemail.com> wrote:
> Hi,
> I'm trying to route packets from ones from one interface to another, 
> without using NAT i.e.
> 
> eth0: 192.168.1.31 (connected to rest of world and DHCP server)
> eth1: 192.168.1.32 (connected to other computers.)
> 
> The other computers would be on the 192.168.1.0/24 subnet and hopefully 
> be able to see all the computers on the subnet.
> 
> I presume I'm going to have to make some sort of bridge, with some 
> forwarding as with IPtables. It would be nice not to have a static IP on 
> the other computers.
> 
> Any suggestions, or discussion of the options, would be gratefully received,
> James

There are two ways to do this:

a) The bridge: You add both eth0 and eth1 to a bridge, which then
gets an IP address from the DHCP server and forwards everything on
the ethernet level.

b) The router: For this to work, you need to divide your subnet into
further subnets (or only use specific IPs behind the gateway) in
order to
 - set up your external DHCP server/router to tell it that it can
   find those IPs behind the gateway.
 - set up your gateway to tell it to forward stuff to those computers
   via eth1.
If this is done, you need to enable IP forwarding via a sysctl call
on the gateway. Here, the forwarding takes place on the IPv4/6 level.

I would suggest to go by a), which is much simpler. If you need more
help with either of them, please feel free to ask.

Best regards,

Claudius
-- 
              A board is the planck unit of boredom.                
http://chubig.net                          telnet nightfall.org 4242

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