Routing to IP subnet broadcast address

Routing to IP subnet broadcast address

Post by Vicky Larmou » Tue, 10 Sep 2002 23:00:15



[posted on behalf of a colleague:]

I'm working on a system where a host sends a UDP message to all
hosts on a remote subnet using the subnet broadcast address ie
host 169.254.x.y sends to 172.16.255.255. I have a Linux box
attached to both subnets acting as a router.

Using tcpdump, I can see the UDP message being received by the
Linux box, but nothing appears on the 172.16.n.n network.
Sending to an ordinary host works eg 169.254.x.y to 172.16.p.q (ip
forwarding is on, routing seems to be correct).
I'm using kernel 2.2.18pre21 (Debian 2.2r2)

Is there something I can do to change this?
Would the iproute2 tools solve this problem? (although I'd rather
not recompile the kernel unless necessary).

Note: I'm NOT trying to route _ethernet_ broadcasts, and I'm NOT
using the IP broadcast address (255.255.255.255).

Thanks,
Peter

[Note: please either follow-up here or e-mail replies directly to
Peter [dot] Laird [at] CambridgeConsultants [dot] com. Thanks! - V]