multicast and multiple nics

[Giulio Ferro]

This is something that's really been puzzling me lately...

Freebsd 8 beta amd64 recently updated

The box has 2 nics:
(internet inteface)
em0 : 192.168.1.1, netmask 255.255.255.0

(lan interface)
re0 : 192.168.2.1 netmask 255.255.255.0 (lan interface)
        192.168.2.2 netmask 255.255.255.255 (alias 0)
        192.168.2.3 netmask 255.255.255.255 (alias 1)

I want to run ushare (/usr/ports/ushare). This program sends
multicast packets to multicast address 239.255.255.250

The packets should go to the lan, so I add the route:
route add 224/4 -iface re0

In order to do the test I switch off the firewall (/etc/rc.d/pf stop)

I start the service, but no packets can be seen leaving the interface re0
with tcpdump.

Even If I ping a multicast address directly I can see no packets at all:

ping -I 192.168.2.1 239.255.255.250

I can't really understand why this doesn't work. I've also tried to enable
multicast routing (mrouted), just defining the interfaces I want to use
in /etc/mrouted.conf, but no luck. I'm not even sure if mrouted should be
needed in this setup, anyway...

Can someone point me what I'm doing wrong?

Thanks.