[TriLUG] spoofing mac addresses

[Aaron S. Joyner]

paul wrote:

>Hi all, 
>
>I have 2 nics in a machine, one of which serves a backend private
>address, and the other of which is on the front end with 13 addresses
>aliased to it (ie: eth1:1, eth1:2, etc...). I think what I am finding is
>that I can only spoof the mac address on one of the physical interfaces
>(eth0 or eth1), and not individual mac addresses for each ip address (on
>the aliases eth1:1..). Is that the case or does someone know of a way to
>make this work?
>
>thx,
>
>-paul
>
>  
>
I believe you're confusing concepts here.  A physical Ethernet card 
*should* only have one MAC address.  Now I stress the *should* because 
that's the way things were originally intended to be - ARP (Address 
Resolution Protocol) can map as many addresses as you'd like with that 
single MAC address, but a MAC is supposed to correspond to a physical 
piece of hardware (your Media Access Controller).  You can of course 
bend the rules, put the card into promiscuous mode, and respond to 
traffic for more than one MAC address, but that's not something most 
Ethernet hardware will do on it's own, it requires a healthy dose of 
software magic.  I do not know off-hand what readily-available tools 
there are to do this w/ Linux, but perhaps someone else will respond 
with more insight, or confirming what it appears you have started to 
discover, will be helpful.

Best of luck,
Aaron S. Joyner