Re: [lwip-users] MAC Question????

[H. Peter Anvin]

K.J. Mansley wrote:
> On Wed, 2004-03-31 at 18:37, Kelly Chan wrote:
> > Hello,
> >
> > We can use ARP to query MAC address for a particular IP? How about the
> > other way such that is there any protocol or broadcast messages we can
> > use to query IP address for a particular MAC address?
>
> Yes.  Funnily enough it's called Reverse ARP (RARP):
>
> http://foldoc.doc.ic.ac.uk/foldoc/foldoc.cgi?query=rarp&action=Search

Except RARP isn't really supported on most networks.  It's really more 
of an early alternative to BOOTP (which then, in turn, got superceded by 
DHCP.)

For a MAC address for an already configured host on the local network, 
one can send a ICMP ECHO (ping) packet with the appropriate unicast MAC 
address and the broadcast IP address.  You should get a response back, 
at which time you know the MAC.

        -hpa