On Tue, Mar 29, 2011 at 10:33:09PM +0000, Grant Edwards wrote: > Somebody I work with has spent the last three days trying to send UDP > multicast packets using eCos and the FreeBSD network stack. > > After quite a bit of trial-and-error we've discovered that you can't > send UDP multicast packets without configuring a valid gateway > address. > > That seems broken to me. > > What are you supposed to do if you're on a strictly local network that > doesn't _have_ a gateway? [That is the case for many of our products.]
Hi Grant In the Linux world you have to do something like: ip route add 224.0.0.0/4 dev eth0 before multicast works. The kernel has no idea which interface to send the multicast packet out, unless you add a route like this. Maybe in the BSD world, instead of defining the interface directly, you give the local IP address on the interface? Maybe this helps: http://www.freebsd.org/doc/handbook/network-routing.html In the example routing table is: 224 link#1 UC 0 0 Andrew -- Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
