Author: Vic Date: To: hampshire Subject: Re: [Hampshire] One box, 2 NICs - but with the same MAC address
> The idea makes me cringe, but someone has decided that it would be a > "good" idea (for certain values of good) to have 2 network ports on the
> same system with the same MAC & IP addresses
I have a nasty suspicion that whoever thought this was a "good" idea
doesn't understand nearly as much about networking as he thinks he does.
> I don't think this is sane, sensible or
> conforming to general networking principles; am I being fair to refuse it?
Absent some extraordinarily compelling reason - yes.
It *is* possible to have two NICs with the same IP address on the same
network. It's rarely very useful - I once used it to demonstrate
hot-plugging of USB devices. Off the top of my head, I can't think of a
decent reason to use it in a production environment.
Duplication of MAC addresses is another matter, though; MAC addresses are
*supposed* to be unique. I'd have to read my networking texts to be sure,
but I suspect you're going to leave yourself in the situation where the
behaviour of the system depends on the undocumented behaviour of each
component; I really, really wouldn't go there.
> (well, they'll never be on the same physical network)...
Two identical IP addresses but on different networks? How exactly do you
intend to run the routing table?
Don't walk away from this. Run. Perambulate as fast as the local gravity
will allow.
> I can see all sorts of problems, and I maintain that it is the
> responsibility of an upstream router to perform any NAT that is required
> (along with the redundancy switching).
Generally speaking, yes.
If it's not confidential, what's the application?
> And if I'm being more-than-usually unreasonable, is there a way of
> achieving it without rewriting chunks of the stack?
Anything you might get going in the short-term is likely subject to total
collapse as soon as any component of the system changes - including things
like version changes.
Perhaps I'm missing something vital, but this looks like the odds-on
favourite for the Dumb Idea of the Year competition...
