try this:
>show interfaces <name> extensive | match packets
You can specify an interface name of leave it off. This should show you multicast, unicast and broadcast
Now that will not tell you if it is excessive, since excesive would be dependent on the particular network. You would need some other network monitoring device to check traffic types over a period of time and at different time intervals to see the levels. It would also of coure depends on if the particular environment is using applications that generate these types of traffic.