Well, after a long debugging session I finally found what is going wrong! It is not this multicast bit. In fact, ampr-ripd sets it while initializing in multicast mode. The cause of my problems was that the same IP address is used on different interfaces. I have my address 44.137.40.2 on tunl0 but also on a tun interface that provides a tunnel to locally running KA9Q software, which uses address 44.137.40.1 When initializing, ampr-ripd joins multicast group 224.0.0.9 with address 44.137.40.2, but I finally found that this is happening on the tun interface and not on the ipip tunl0. This can be seen using "cat /proc/net/igmp". When I start ampr-ripd after creating tunl0 and before the tun is brought up, it works OK. The 44.137.40.2 address still is unique at that point, and the group is joined on the correct interface. I still have to decide what permanent strategy to use. Maybe I need to allocate another address... Rob