Re: Manually controlling ARP requests

From: Michael AKA Slowhand (slowhand_at_darknet.dk)
Date: 01/21/04 

Date: Wed, 21 Jan 2004 02:46:12 +0100

"Lew Pitcher" <Lew.Pitcher@td.com> skrev i en meddelelse
news:ilbPb.10525$cQ6.321545@news20.bellglobal.com...
> Michael AKA Slowhand wrote:
>
> > "Lew Pitcher" <Lew.Pitcher@td.com> skrev i en meddelelse
> > news:81iNb.2052$c1.345205@news20.bellglobal.com...
> >
> >>David Anderson wrote:
> >>
> >>
> >>>Hi all,
> >>>
> >>>For I program I am writing, I need to be able to retrieve the MAC
> >>> address
> >>>for any IP address I receive (the ability to communicate with the said
> >>> IP
> >>>directly is implicit in the environment I work in).
> >>
> >>One question: will the partner systems (the "IP addresses you receive")
be
> >>restricted to IPs on your subnet, or can /any/ IP (on your subnet or
not)
> >> be a candidate.
> >>
> >>If /any/ IP address can be a candidate, then you won't be able to get a
> >> 100%
> >>solution, as ARP only covers the NICs on your subnet (your LAN segment,
> >>really, unless your bridges enable ARP passthroughs). The other IP
> >> addresses
> >>will all have the NIC address of your gateway, and not their own NIC
> >> addresses.
> >
> > I assume you can do this with raw sockets however this works different
of
> > different dists of linux.
> > Like PING (using raw) is able to send an echo which is routed.
> > Maybe it is your gateway MAC address you get.
> > I would like to hear the answer!
>
> You will never get an ARP that carries an address from outside of your
> subnet. That's guaranteed.
>
>
>
>
> --
> Lew Pitcher, IT Consultant, Application Architecture
> Enterprise Technology Solutions, TD Bank Financial Group
>
> (Opinions expressed here are my own, not my employer's)
>

Then Iīve learned something today!
Nice!
Canīt you fetch it from the PDU header received from a host in another
network?
Arenīt the MAC address stored in one of the headers? or is it only the
IPaddress?