TELECOM Digest OnLine - Sorted: Re: Change MAC Address Can Change IP Address of a Machine?

Re: Change MAC Address Can Change IP Address of a Machine?

Steve Sobol (
Sat, 01 Oct 2005 09:14:55 -0700

John Levine wrote:

>> Is there any way to change the MAC address of a machine? IP address is
>> assigned by ISP. My understanding is that IP address is based on the
>> MAC address of a machine, is that correct concept?

> No. Your IP address has nothing whatsoever to do with your MAC
> address.

If you're using DHCP, an IP address X is assigned to the card with MAC
address Y and changing the MAC then renewing your lease is almost
guaranteed to change your IP address. If the DHCP server is set to
assign a static address to your computer, it does so by associating
the static address with the MAC address.

> Your ISP assigns it from their pool of available addresses.
> On my tiny network, when someone plugs in a new computer, it just
> assigns the lowest numbered unused IP address.

Yes, but while you have that address it IS associated with your MAC
address. I think we're discussing two different OSI layers, though.

Steve Sobol, Professional Geek 888-480-4638 PGP: 0xE3AE35ED
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