Hi, Is there any portable way (by using boost) to send multicast messages through all network interfaces available on the host? I have managed to do it by setting outbound_interface option on the socket. However, how can I know which if_index are available? Also, it only works for IPv6. If I set a IPv4 address it always use the same interface. Any suggestion? Next is the code I'm using: // DATA HERE... ip::udp::socket sock(io); sock.open(ip::udp::v6()); // Set socket flags sock.set_option(boost::asio::socket_base::reuse_address(true)); if (strcmp(dst_ip, "ff02::1") == 0) { boost::asio::socket_base::broadcast option(true); sock.set_option(option); } sock.bind(ip::udp::endpoint(ip::address_v6::any(), src_port)); for(int i = 1; i <= 5; i++) { try { sock.set_option(ip::multicast::outbound_interface(i)); sock.set_option(ip::multicast::enable_loopback(false)); ip::udp::endpoint ep(ip::address::from_string(dst_ip), dst_port); sock.async_send_to(boost::asio::buffer(sbuff, slen), ep, boost::bind((&send_handler), placeholders::error)); } catch(...) { return; } }