Re: Find out the subnetting of a company

From: J.A. Terranson (measl_at_mfn.org)
Date: 07/20/04

  • Next message: Volker Tanger: "Re: Find out the subnetting of a company" 
    Date: Tue, 20 Jul 2004 11:22:32 -0500 (CDT)
To: Miles Stevenson <miles@mstevenson.org>

    On Mon, 19 Jul 2004, Miles Stevenson wrote:

    > Usually, the best way to map out how a chunk of address space has been
    > subnetted, is by finding out which addresses are used for broadcasting. This
    > is a trivial task for a tool like nmap, which will notify you when it has
    > stumbled upon a broadcast address.
    >
    > Once you have found a broadcast address, you know that you have the "top end"
    > of a subnet.

    Dangr Will Robinson!

    This is not necessarily so. Early BSD and BSD derived systems/devices may
    also answer to broadcasts on the "lower end". Historically, the broadcast
    was originally designed to *be* the same as the network address, it is
    only recently that the last address has become the standard.

    There are any number of older, and in somecases (like the Nortel CVX call
    concentrators) newer devices answering on both the top and bottom
    addresses. 

    -- 
Yours,
J.A. Terranson
sysadmin@mfn.org
0xBD4A95BF
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  • Next message: Volker Tanger: "Re: Find out the subnetting of a company"

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