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Old 08-30-2004, 09:36 PM   #1
Registered: Jul 2004
Location: Milpitas, California
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NIC hardware address

Hello all. I am wondering why do certain networks insist on you registering your hardware (MAC) address of your network device before you are allowed to access the LAN. How unique are these addresses and can they be falsified so that I don't need to register? Don't worry about
me trying to do anything nefarious.
Thanks for any help,
Old 08-30-2004, 09:39 PM   #2
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because they are pretty hard to change and are completely unique.
Old 08-30-2004, 10:03 PM   #3
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Pretty hard to change? quite to the contrary

Networks require you to register your MAC because they assume most people don't know how to change them and they want some kind of per-machine tracking. By default each machine has a unique MAC, but that doesn't mean you can't change that Some networking devices will even let you assign multiple MACs to one device, and permanently change your MAC (in the firmware).
Old 08-31-2004, 01:25 AM   #4
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To change your mac address:
ifconfig eth0 hw ether <mac address>

The MAC address is supposed to be unique. When they are not unique, you get problems similar to what you see when you have duplicate ip addresses - only harder to track down.
Old 08-31-2004, 04:41 PM   #5
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Ok. But if I connect using dhcp, will they catch me with a duplicate MAC address?
Thanks again.
Old 08-31-2004, 06:44 PM   #6
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Apart from the above, the reason could also depend on what hardware you're connecting to, and under what circumstances. Many Cisco switches that support VLANs can be configured to assign a given MAC address (and therefore, logically, a certain machine) to a given VLAN. This, to my mind, would only really be useful in a situation where machines are moved around a lot.
Old 09-01-2004, 04:39 PM   #7
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lots of routers have mac address cloning to fool your ISP!


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