Another problem with a hub is that all data is transfered to all ports at once, which results in that you have a total of 100mbit to all ports, while a switch gives 100mbit per port. (assuming that you are using 100mbit NIC and switch/hub of cource). If you buy a 24 port 100mbit hub, and everyone uses full capacity on their port they will only be able 100/24mbit, about 4mbit.
Also, that statement that coore made is not true for all hubs, mine can handle both 10 and 100mbit cards simoultaneously.
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