Re: Using ARP to map a network

[sith () sithender com]

On Tue, Feb 04, 2003 at 06:36:59PM -0500, Jason Lewis wrote:
> I have searched and can't seem to find any tools to help map a network
> based on ARP tables.
>
> It seems to me, I could take ARP tables from several machines and build a
> network map.  

Yes, you could at least see what machines were up on the network.  One thing
I sometimes do is ping the broadcast address, and then save the arp table,
but that is obviously not passive, hehe.

> If machines were behind a router the ARP tables would show
> multiple IP's with the same MAC.  With enough ARP tables, wouldn't I be
> able to build a map?

You won't have listings in your arp table beyond your subnet.

> Is my theory flawed?
>
> My goal is to do passive network mapping based on any local information I
> can obtain from computers or network devices.  Anyone have any ideas?

Unless you have static arp tables, you won't have things in your arp tables
for usually more than a few minutes, so It's probably just as easy to get
this information listening to network traffic, ie. logging the original arp
replies.

Hope this helps,

sithEnder

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