On Fri, 20 Aug 2004, Thomas Hertz wrote:
> > Am Fr, den 20.08.2004 schrieb Thomas Hertz um 8:34:
> > > I'm in the process of changing my ISP from DSL with one static IP to
> > 100mbps
> > > Ethernet with five dynamic, DHCP assigned, addresses. I'm not quite sure
> > how
> > > this would work, but does anyone know of a way to assign more than one
> > IP to
> > > the same physical interface? It would be neat to use 1:1 NAT.
> > Yes, you have to use proxy arp. Search this list for or for really
> > understanding take a look at
> > http://www.thinkingsecure.com/docs/TCPIP-Illustrated-1/arp_addr.htm#4_6
> > Ciao ...
> > ... PIT ...
> [Thomas Hertz once mumbled:]
> That would be a breeze if my addresses were static, but I've yet to find a
> dhcp client that supports several _dynamic_ addresses! It should even be
> possible using a client identifier instead of the interface MAC (if the dhcp
> server supports it, that I do not know).
That might be iffy. The Microsoft-originated feature to key on host names
instead of MAC addresses violated the intent of a DHCP option rather than
change the client identifier. :-)
There is a way this *could* work reasonably, but not with existing
1) Use ARP to obtain the MAC address of the intended real destination.
2) Use that as the identifier for DHCP. It should be guaranteed unique.
3) If DHCP succeeeds, install a Proxy ARP mapping on the WAN side.
4) Poll the server periodically, and undo all the above if it goes away.