After some more checking.. and confusing results. I realized my packet capturing would throw the nic on the linux box into promiscuous mode. Thus, all my traffic monitoring was making the nic listen to the port 5353 stuff to 18.104.22.168. So, when I was monitoring, it always worked. Manually sticking the card into promiscuous mode works. So, in my case, it wasn’t a firewall, it was the nic just not accepting traffic that wasn’t addressed to its ip or broadcast range. In this case, iptables rules didn’t help since iptables wasn’t blocking anything to start with. Most linux distros have promiscuous mode disabled by default… I’d prefer not to use promiscuous mode.. I may come up with a workaround.. if I do I’ll post it here.
Aaah.. yeah, I think that’s a card driver thing. Some drivers don’t do multicast. I’ve only ever seen that on the linkstations, though. Do you have a different card you can use?
p.s. — what kind of network card is it? Something borderline supported? Like a sis900 or nforce?