hacmp广播地址问题

In SMIT, select Cluster Nodes and Networks > Initial Cluster Configuration (Typical) > Setup a Cluster, Nodes and Networks and press Enter.Complete the fields and press Enter.Press F3 to return to the previous SMIT panel and select Define Repository Disk and Cluster IP Address.Complete the fields and press Enter.Note: The default value for the Heartbeat Mechanism field is unicast. If you select multicast for the Heartbeat Mechanism field, you must verify that your network devices are configured for multicast communication.
执行上述步骤ok，但是ifconfig -a在网卡上看不到广播组地址是怎么回事呢