[sclug] Forwarding broadcasts

[Paul Weaver]

On Fri, Jan 07, 2005 at 09:16:51PM -0000, Roland Turner (SCLUG) wrote:
> Paul wrote:
> 
> > I know you're not meant to do it, however we've had a specific need to
> > forward broadcasts from one subnet onto another.
> 
> There are a number of approaches. Can you provide some more clues about
> what it is that the requirement is aiming to achieve (and that could not
> be achieved, e.g. with a switch)?
> - Raz

6 8 bit networks - 192.168.1.0 through 6.0. All of them have a suite of
computers that find out about each others capabilities via broadcast packets. 
Occasionally one computer wishes to find a computer on another network, so 
it sends a broadcast to that network. 

Normally, 192.168.1.100 will send packets to 192.168.1.255 and receive
replies from 101 (sharer), 102 (database), etc.

At the same time 192.168.2.100 will send packets to 192.168.2.255 and
receive replies from 101 (sharer), 102 (database), etc.

These networks are normally kept seperate, and should be independent
from each other as much as possible.

However, 192.168.1.100 wants to send a packet to network 2's database.
It has no idea what that is, except it will respond to 192.168.2.255. It
sends the packet to 192.168.2.255 and this should be routed.

The kernel wont forward these packets as they are destinied for broadcast 
addresses.