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Switches are multiport bridges.
In many ways I like the 2nd better but 3rd will do you. This is your livelihood and you had all better be familiar with the material in the Tannenbaum book whether you read his book or another general text on computer networks. I would also hope that anyone trying to be a systems administrator would be acquainted with a general text on operating systems theory. You can spoof Ethernet addresses, I've seen it done.