IP Multicast

["Neel Sheyal" <neelsheyal%gmail.com@localhost>]

Hi,

    I have two netbsd hosts both with two NICs.

HOSTA: ex0: 192.168.21.2/24  and ex1: 172.16.18.2/16
HOSTB: ex0: 192.168.22.2/24  and ex1: 172.18.20.2/16

There is an application sending multicast traffic on hostA to
239.198.1.2. There is another application on hostB which is subsribing
to this group.

The application on hostA or hostB does not specific the outgoing
interface for sending traffic or joining. I have also not send the
routing table with the multicast group information.

How does the OS know which interface to send the multicast traffic as in hostA?

How does the OS know which interface to subscribe to for receiving
multicast traffic as in hostB?

Thanks,
~~Neel