I'm working with the Multicast receiver example at: http://www.boost.org/doc/libs/1_35_0/doc/html/boost_asio/example/multicast/r... Notice that you specify the listen_address as you create the endpoint that is bound to the socket. Later when you call socket::set_option with the multicast_address, I would expect the listen_address to be honored. The current implementation uses INET_ANY for the interface in the multicast subscription. This means the multicast messages may arrive on one interface while you are listening for them on another one. I can't think of any case in which you would want to specify an IP for the receive, but not for the join_group. Workaround: There is a different constructor for the join_group object that does produce the desired behavior, but it is not obvious that you should need it. Also it does not accept boost::asio::ip::addresses as arguments (which would make sense) but requires that you "convert" them to ip4 (or ip6) addresses. Seems awkward. Dale