[nzlug] Routing UDP broadcast packets

[Toby Collett]

Hi all,
I have a piece of software (PLC programming) that uses UDP broadcast for 
discovering PLC resources. The problem I have is that the PLC resources 
are located on a different subnet (wifi) behind a shorewall/iptables 
firewall. The software is capable of looking on a remote subnet for the 
devices but the firewall wont route the traffic (quite probably by 
careful design).

So some detail. broadcasting machine is on 10.99/16 subnet and target is 
on a 10.77/16 subnet. The broadcaster is sending to 10.77.255.255, but 
the request is not routed. The same happens with broadcast pings, 
tcpdump shows the traffic on the local interface on the firewall but not 
on the destination.

Does anyone know what rules/OS (linux/ubuntu) configuration is needed to 
achieve this? or if it is possible at all?

Thanks,
Toby