Forwarding broadcast traffic

Jon Masters
2001-03-03T10:53:12Z

Hello,
I have a brain-dead application here which relies on broadcast
traffic for client/server discovery and I have a question with regard
to forwarding broadcast traffic.

A small part of my local LAN looks like this:

REST OF LAN
|
| (router eth1)
|
masquerading
router (kernel 2.2.14)
|
| (router eth0)
|
desktop (private IP)
boxen (kernel 2.4.2)

* upgrading the router is not a problem[0].

I wish to have the router forward certain broadcast traffic coming
from either side out to the other (as well as itself).

e.g. on desktop a broadcast udp packet (with a specified port) needs to
go not only to itself and the router but also the "REST OF LAN" part
too - and vice versa. Removing the router is not an option.

I know this isn't a *nice* idea and ordinarily I wouldn't be jumping up
and down suggesting one throws broadcast traffic around however I need
to do this for various reasons and the solution appears to be
non-obvious at least to me[1].

I have considered the idea of creating a transparent bridge however I
would really rather not do that here for various reasons.

I have posted this message to groups elsewhere however I have not yet
had any useful responses beyond basic instruction of IP forwarding,
etc. which is not what I need here :P

Any ideas? I think this one has come up before but I could not find a
helpful answer in my archives.

Appreciate your time,
--jcm

P.S. My lkml feed at home is great but here it is not so could you
please CC me on replies thanks.

[0] Yeah, yeah, I know 2.2.14 is old but it's an old router and when I
move that box over to Debian I'll upgrade the kernel at the same
time :P
[1] either due to general stupidity or tiredness, or both.