Media-One Express, IP Masquerading

[mikebw at bilow.bilow.uu.ids.net (Mike Bilow)]

David Kramer wrote in a message to Mike Bilow:

 DK> I just wanted to add a reminder to this one though; since
 DK> their DNS is tied to the network card hard-coded address,
 DK> you need to move the very same network card from your Win95
 DK> box to the linux box.  Right? 

DNS maps domains to network (IP) addresses.  It knows nothing about MAC
(Ethernet hardware) addresses.

DHCP is what you are thinking about.  It maps network addresses to MAC
addresses.  I believe that some systems do tie the network address assignment
to a particular MAC address.

However, instead of moving the card, it is certainly possible to command the
use of a different MAC address in software.  Although the MAC address is burned
into the card, it is simply read by the driver, which is then free to use it or
any other on the wire.

In the ordinary world, we use Address Resolution Protocol (ARP) to negotiate
very temporary (15 minute) mappings between network and MAC addresses,
specifically in order to avoid tying to a particular Ethernet card.  Once DHCP
assignment is completed -- which does depend upon the specific MAC address of
your specific card -- then ARP may handle everything fine until it comes time
to assign a new address using DHCP.
 
-- Mike