Re: Manually controlling ARP requests

From: Lew Pitcher (Lew.Pitcher_at_td.com)
Date: 01/20/04 

Date: Tue, 20 Jan 2004 09:57:16 -0500

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)

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