enable multicast/broadcast at adhoc mode

Hi, I am trying to use several computers and router boards to form an adhoc network. However, the multicast/broadcast function is not supported, though I implement the mrouted (https://www.freebsd.org/doc/handbook/network-routing.html). The phenomenon is that we ping multicast ( or broadcast (XXX.XXX.XXX.255) address, no route and no request. Do I need to configure more? By the way, when I connect the device to wifi, the multicast/broadcast is enabled, but not enabled at adhoc mode.