Multiple ethernets on one cable modem

[mcmanus at AppliedTheory.com (Patrick McManus)]

In a previous episode tkeller at helpdesk.mso.stratus.com said...
:: 
:: At least for Mediaone this is always the case, they snatch your MAC
:: address and use it in their DHCP server but you can get around this.  If
:: you decide you want to change ethernet cards when you get the new card
:: configured in your machine you can just tamper with the rc.d scripts that
:: bring up the ethernet card so that issues 
:: /sbin/ifconfig  eth0 hw ether xx:xx:xx:xx:xx:xx
:: where the xx:xx ... is the mac address that you want to transmit with.

a few caveats: The ability to change MAC addresses is a NIC feature,
not an OS feature.. (the ifconfig is just a hook for it).. it's
extremely widespread, but not universal. (I can't remember which one,
but I've had a NIC that wouldn't do it several years ago.)

* obviously you better make sure that your old NIC is either not in
  use or mapped to something else after doing this... even if they
  aren't on the same ethernet segment lots of applications use the MAC
  as a globally unique identifier

* in general, this is very effective if the change is a] temporary, b]
  just for testing, or c] to keep you sane while on hold with m1
  waiting to ask them to make the real change.. Otherwise it's a
  manual state change that's just begging to get screwed up at some
  point and cause you frustrations.. if the change is permament I just
  give them a call.. after they answer the phone (a trial that can be
  anywhere from 30 seconds to 90 minutes) the change only takes 2
  minutes for them to do, and they seem to be well trained on how to
  do it.

-P
-
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