question about multicasting

Helllo I am new to networking concepts, Have been reading the site, its remarkable to say the least. The only concept I have a little difficult with grasping is this:

When it comes to multicasting as opposed to Broadcasting, a packet is recieved by a computer with a MAC/IP mapped destination Mac address, but how does the machine know its not supposed to recieve the multicasted message, as opposed to a broadcast where every machine will recieve the package. To rephrase that again, when a multicasted package is sent out, its asserted to represent a multicast package, but doesnt every machine recognize the 01 bit the same way, and understand its a multicast, moving onto the networking layer, checking IP, which will be recognized as a multicast package as well. How is a machine excluded from a multicast on a network? I hope my question is clear enough!

hi,

if i understood your question i think your asking what's the difference between a multicast and a broadcast.

well multicasting is sending data or message to a selected group while a boradcast sends data/message to everyone.connected within the network.

i think when you send a mulitcast packet over the network, each host on the network analyzes the packet sent. and since the packet contains information regarding to which IP and MAC address the packet is intended to, the machines that recognize that the packet is not for them to receive so they reject it until the packet intended for the machine or host is receive. (as this is what what i understand although i maybe wrong :roll: )